ORCID Profile
0000-0002-8460-3604
Current Organisation
Monash University
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Publisher: Springer Science and Business Media LLC
Date: 1993
DOI: 10.1557/PROC-321-579
Abstract: We report in situ high resolution transmission electron microscopy studies of NiSi 2 -Medi-ated crystallization of Amorphous Si. Compared to conventional solid phase epitaxy of (111) Si, an enhancement of the growth rate by three orders of magnitude was observed and high quality twin-free needles of Si were formed. Crystallization occurred via a ledge growth mechanism at the epitaxial Type A NiSi 2 /crystalline Si (111) interface. A Model for NiSi 2 -Mediated crystallization of Amorphous Si involving the passage of kinks along ledges at the NiSi 2 /crystalline Si (111) interface is proposed.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-115-63
Abstract: Techniques for the preparation of specimens for Transmission Electron Microscopy analysis are described. Cross-sectional specimens of insulator/semiconductor heterostructures have been successfully prepared. The problem of differential thinning rates and interface amorphization during argon ion-milling have been overcome using low argon ion accelerating voltages and shallow angles of incidence. Techniques for preparation of plan view specimens include the preparation of silicon substrates for in-situ crystal growth in an ultrahigh vacuum Transmission Electron Microscope.
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1557/PROC-139-351
Publisher: Cambridge University Press (CUP)
Date: 1988
DOI: 10.1017/S0424820100104509
Abstract: Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and Hg x Cd 1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x. Two major sources of precipitation can be identified in II-VI materials (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1557/PROC-116-403
Abstract: By nature of their high degree of crystalline perfection, epitaxial insulators and metals on semiconductors are structurally characterizable to a considerably greater extent than are polycrystalline or amorphous materials. This offers the possibility of correlating the detailed structure of these thin epitaxial films and their interfaces with their electrical properties. We have recently found evidence for the influence of the atomic structure of the CaF 2 /Si(ll1) interface on its electrical properties. Wehave also studied the structural and electrical properties of ultrathin epitaxial cobaltsilicide layers on Si(111).
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1557/PROC-100-87
Abstract: We have measured the radiation-enhanced diffusion of Au in amorphous Si in the temperature range 77–700 K. Gold was implanted to depths of 500Å at concentrations of an atomic %. The s les were than amorphized to depths of -2μm using MeV Ar implants at liquid nitrogen temperature. Radiation-enhanced diffusion was induced by a 2.5 MeV Ar beam at doses of 2×10 16 −2×10 17 /cm 2 and dose rates of 7×10 12 −7×10 13 /cm 2 sec. The diffusion coefficients show three well defined regions. At temperatures K diffusion is essentially athermal and due to ballistic mixing. At temperatures between 400K and 700K the diffusion, which is considerably enhanced over the usual thermal values, has an Arrhenius behavior with an activation energy of 0.37 eV. At higher temperatures thermal diffusion, with an activation energy of 1.42 eV, dominates.
Publisher: AIP Publishing
Date: 23-02-1987
DOI: 10.1063/1.98175
Abstract: The heteroepitaxial quality of (100) Si films on (11̄02) sapphire substrates (SOS) as measured by Rutherford backscattering (RBS) and x-ray pole figure analysis is improved by a rapid thermal anneal (RTA) after deposition which brings the Si temperature above 1350 °C for at least several seconds. For a 6000-Å (100) SOS film the (100) aligned to random RBS yield improves from 10% and 54% at the front and back interfaces, to as low as 3.2% and 13% after the RTA. The microtwin volume shows a corresponding decrease to under 1% from the as-grown value of 2.7%. A model based on isothermal solid phase epitaxial regrowth from the untwinned material near the front surface is proposed to account for these results.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-389
Abstract: We have studied the dependence of the structural and electrical properties of ultrathin cobalt silicide films on the annealing temperature and deposited Co thickness. We recently reported that coherent, electrically continuous films of CoSi 2 could be grown on Si(111) with thicknesses as small as 1 nm. 1 The thinnest of these films had a high density of pinholes which covered about 20% of the area of the substrate. The resistivity of the films increased dramatically with decreasing thickness in a manner which was qualitatively consistent with quantum size effects. In order to investigate the dependence of both the pinhole density and the resistivity of ultrathin CoSi 2 films on Si(111), we have deposited different thicknesses of Co onto near room temperature ( °C) Si(111) substrates and have annealed the s les at different temperatures in order to study the effect of silicide formation conditions on the structural and electrical properties of the resulting films. Co layers were deposited onto Si(111) wafers in a molecular beam epitaxy apparatus as described previously. 1 In our earlier work, CoSi 2 was formed by heating the s le to ∼600°C for a few seconds after Co deposition. Because higher temperature anneals are known to lead to pinhole formation in thicker films, 2 annealing temperatures in the present experiments were constrained to be 600° or less. The reaction time was on the order of 5 minutes. The layers were examined using plan-view transmission electron microscopy (TEM) in order to avoid beam heating and ion beam mixing effects which might cause artefacts in cross-section TEM observation. The results of our experiments are summarized in Figure 1. The figure indicates the silicide phases found in a film as a function of deposited Co thickness and annealing temperature. The numbers in each square correspond to the residual resistivity, ρ o , measured for each film. Perhaps the most striking finding of this study is the abrupt change in the structure of the films between 0.7 and 1.4 nm of deposited Co. For all temperatures investigated (including near room temperature), films formed by depositing less than 1 nm of Co form CoSi 2 immediately upon deposition. (For films approaching this thickness, there is also a small amount of Co 2 Si which persists at all temperatures
Publisher: Cambridge University Press (CUP)
Date: 08-1992
DOI: 10.1017/S0424820100131498
Abstract: Porous Si has recently been shown to luminesce efficiently in the visible region of the spectrum. This discovery has lead to much excitement at the prospect of developing Si-based optoelectronic devices. However, the mechanism of this visible luminescence from an indirect-gap semiconductor is still the subject of much debate. In addition, the peak wavelength and efficiency of the luminescence is extremely sensitive to the preparation conditions and subsequent treatment of the s le. In this paper, Cathodoluminescence (CL) data are presented to show the degradation of luminescence when the s les are exposed to an electron beam. Porous silicon films were prepared by anodically etching p − Si(001) substrates in a solution of HF: H 2 O:C 2 H 5 OH at current densities of 1-20mA/cm 2 . Cathodoluminescence was excited by electron beam irradiation of the s les in a JEOL JSM6400 scanning electron microscope (SEM) equipped with an Oxford Instruments wavelength-dispersive CL system and liquid He cold stage. Monochromatic CL images were obtained in the wavelength range 600-800nm.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-265
Abstract: The growth of ultrathin epitaxial CoSi 2 layers on Si by molecular beam epitaxy has been studied. This paper briefly outlines recent progress in the growth on Si(111) substrates. New results on the growth of epitaxial CoSi 2 on Si(100) are also presented.
Publisher: Trans Tech Publications, Ltd.
Date: 03-1994
Publisher: Elsevier BV
Date: 03-1989
Publisher: Cambridge University Press (CUP)
Date: 08-1992
DOI: 10.1017/S042482010013136X
Abstract: The solid state transformation of amorphous silicon (a-Si) to crystalline silicon (c-Si) is a first order phase transformation which is driven by the difference in free energy between the amorphous and crystalline phases. The crystallization occurs at temperatures of 500-700°C which are readily accessible with commercial specimen heating stages for the transmission electron microscope (TEM). In this paper we study the a-c phase transformation dynamically by utilizing the powerful technique of in-situ TEM to monitor the nucleation and growth kinetics of thin films of Si. The propagation of a moving a-c interface is presented and an activation energy for crystal growth is obtained. 400Å of a-Si was prepared by electron beam deposition of Si at room temperature on amorphous Si 3 ,N 4 “window” substrates which required no additional s le preparation for TEM. The s les were examined in a plan view orientation to minimize surface effects on the crystallization process. The a-Si films were annealed by in-situ heating in a Gatan single-tilt hot stage which has a temperature accuracy of ±25°C. Crystallization occurred at ∼700°C with the formation of small crystallites which grew to consume the entire amorphous film. Fig. 1 shows a partially transformed region of a-Si after annealing at 710°C for 6 mins.
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1557/PROC-82-335
Abstract: High resolution electron microscopy (HREM) is recognised as a powerful technique for thedetermination of atomic structures at crystal defects and interfaces. The application ofHREM to the study of insulator/semiconductor and metal/semiconductor interfaces is of particular technological interest. Correlation of electrical properties withinterface structure has been performed, taking advantage of the resolution available in the JEOL 4000EX. Images are usually obtained in a projection, however in the JEOL 4000EX (point-to point resolution .7A). we have imaged semiconductor interfaces in the =direction using the (220) planes of 1.92Å spacing revealing all atomic columns in silicon, permitting “structure images” of interfaces to be obtained. Two types of interface have been studied at .9Å resolution. The roughness of the important crystalline Si/amorphousSiO 2 interface observed in implanted buried oxide layers and after wet and dry oxidation of silicon is relevant for the correlation of carrier mobilities with interface structure. Analysis of both the NiSi 2 /Si(100) and AI/AIGaAs(100) crystal/crystal interfaces where a periodic structure is observed in the plane of the interface allows the use of rigid shift measurements and multislice image calculations to determine an atomistic model. The influence of the NiSi 2 /Si interface structure on the Schottky barrier height is discussed.
Publisher: AIP Publishing
Date: 19-10-1987
DOI: 10.1063/1.98697
Abstract: Scanned zone-melt recrystallization (ZMR) of amorphous Si 1-μm films on SiO2 results in subboundary-free material provided the thermal gradient along the scan is reduced to 4 K/mm or less. Below this value the usual ZMR subboundaries consisting of networks of in-plane edge dislocations are replaced by rows of threading dislocations. We account for the two kinds of crystallization by extending the faceted solidification model that we developed previously. We consider profiles of the solidification front at the intersections of {111} facet pairs where subboundaries are known to form, and postulate that the profiles are aligned approximately normal to the scan in the high gradient case, but become tilted toward the plane of the SiO2 cap layer for the low gradient case. The tilting accounts in a natural way for subboundary removal and the transition from in-plane to threading dislocations.
Publisher: American Physical Society (APS)
Date: 07-11-1988
Publisher: Cambridge University Press (CUP)
Date: 08-1990
DOI: 10.1017/S0424820100175752
Abstract: Recrystallization of amorphous NiSi 2 involves nucleation and growth processes which can be studied dynamically in the electron microscope. Previous studies have shown that CoSi 2 recrystallises by nucleating spherical caps which then grow with a constant radial velocity. Coalescence results in the formation of hyperbolic grain boundaries. Nucleation of the isostructural NiSi 2 results in small, approximately round grains with very rough amorphous/crystal interfaces. In this paper we show that the morphology of the rccrystallizcd film is dramatically affected by variations in the stoichiometry of the amorphous film. Thin films of NiSi 2 were prepared by c-bcam deposition of Ni and Si onto Si 3 N 4 , windows supported by Si substrates at room temperature. The base pressure prior to deposition was 6 × 10 7 torr. In order to investigate the effect of stoichiomctry on the recrystallization process, the Ni/Si ratio was varied in the range NiSi 1.8-2.4 . The composition of the amorphous films was determined by Rutherford Backscattering.
Publisher: Cambridge University Press (CUP)
Date: 06-08-1989
DOI: 10.1017/S0424820100154251
Abstract: Cobalt silicides can be grown epitaxially on silicon by room temperature (RT) deposition of Co onto in-situ cleaned Si in an ultra high vacuum environment. Post-deposition annealing at ∼550°C leads to the formation of CoSi 2 which exists in two orientations on Si (111), known as type A and type B. The fractional coverage of type A CoSi 2 is critically dependent on the metal thickness. If Å Co is deposited at RT, type B CoSi 2 is formed. For Å Co, intermediate metal-rich silicide phases such as Co 2 Si and CoSi are formed at low ( °C) temperatures. At °C, mixed A+B type CoSi 2 is formed. If higher reaction temperatures are employed, large (∼2000Å) pinholes open up allowing dislocation motion and a conversion of the film to entirely type B CoSi 2 . Epitaxial growth of CoSi 2 on Si (311) has recently been demonstrated. Two orientations, A and B were observed where the B orientation was rotated with respect to the substrate about the inclined (111) axis. Electrically continuous films were obtained at temperatures as low as 500°c with residual resistivities ∽10μΩcm. This work has now been extended to study the effects of substrate orientation on intermediate phase formation in the Co/Si system.
Publisher: AIP Publishing
Date: 09-05-1988
DOI: 10.1063/1.99702
Abstract: Template techniques for Si epitaxy are designed based on the two structures, CoSi2-C and CoSi2-S, of the CoSi2 surface. The different stacking sequences of the two CoSi2 surfaces have led to the growth of single-crystal epitaxial Si layers with either type A or type B orientation on CoSi2(111). The crystalline quality of these Si/CoSi2/Si structures far exceeds that of those reported previously. The orientation of the epitaxial Si overlayer is also found to depend on the strain in the epitaxial CoSi2 thin films.
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1557/PROC-116-439
Abstract: The growth of high quality, thin (14-70 Å) epitaxial CoSi 2 layers on Si(100) substrates have been observed. Three types of films have been grown on the Si(100) substrate pure CoSi 2 (100), pure CoSi 2 (110), and mixed CoSi 2 (100)+CoSi 2 (110). The CoSi 2 (110) can exist in two 90 º rotated variants on the Si(100) surface and these are observed. Methods to isolate the epitaxial orientations are described. Results from in-situ LEED and AES as well as ex-situ RBS and plan view TEM are presented.
Publisher: Cambridge University Press (CUP)
Date: 13-08-1995
DOI: 10.1017/S0424820100136398
Abstract: The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer thus an understanding of factors influencing the defect densities is required. Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).
Publisher: Cambridge University Press (CUP)
Date: 08-1990
DOI: 10.1017/S0424820100176009
Abstract: When CoSi 2 is grown onto a Si(111) surface it can form in two distinct orientations. A-type CoSi 2 has the same orientation as the Si substrate and B-type is rotated by 180° degrees about the [111] surface normal.One method of producing epitaxial CoSi 2 is to deposit Co at room temperature and anneal to 650°C.If greater than 10Å of Co is deposited then both A and B-type CoSi 2 form via a number of intermediate silicides .The literature suggests that the co-existence of A and B-type CoSi 2 is in some way linked to these intermediate silicides analogous to the NiSi 2 /Si(111) system. The phase which forms prior to complete CoSi 2 formation is CoSi. This paper is a crystallographic analysis of the CoSi 2 /Si(l11) bicrystal using a theoretical method developed by Pond. Transmission electron microscopy (TEM) has been used to verify the theoretical predictions and to characterise the defect structure at the interface.
Publisher: AIP Publishing
Date: 24-05-1993
DOI: 10.1063/1.109279
Abstract: The stability of the luminescence from porous Si has been improved by rapid thermal oxidation. As-prepared and oxidized s les have been compared by cathodoluminescence and photoluminescence. Electron beam excitation resulted in rapid decay of the porous Si emission from as-prepared s les. Photoluminescence measurements from as-prepared s les in oxygen showed a similar degradation. In contrast, the rapid thermal oxidized s les showed a dramatic improvement in stability under either electron beam or photoexcitation.
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1557/PROC-74-585
Abstract: From the early work on high dose oxygen implantation for buried SiO 2 formation, it is apparent that the temperature of the Si substrate during the implant has a strong influence on the quality of both the SiO 2 layer and the overlying Si. This, in turn, can be related to the damage from the oxygen implant. For substrate temperatures ∼ 300°C, amorphous Si is created during the implant and leads to the formation of twins or polycrystalline Si during the subsequent high temperature ( °C) anneal. At higher substrate temperatures ( ∼400°C), dynamic annealing eliminates the amorphous Si, but the implanted oxygen appears to segregate during the implant leading to oxygen-rich amorphous regions imbedded in regions of crystalline material. As the amorphous regions start to coalesce and form SiO 2 during the high temperature anneal, they trap crystalline Si which cannot escape by diffusion. This process can be circumvented by using a randomizing Si implant to change the damage structure from the oxygen implant before annealing. We have seen these effects clearly in sub-stoichiometric implants, and believe they are also operative during stoichiometric implants.
Publisher: AIP Publishing
Date: 22-02-1988
DOI: 10.1063/1.99393
Abstract: The growth of ultrathin (& Å thick) uniform CoSi2 layers at low temperatures (& °C) has been reported recently. Pinholes are formed in these silicide layers when the temperature is raised to above ∼550 °C. An important driving force for the generation of pinholes has been identified as a change of the surface structure from CoSi2-C, stable at low temperature, to the high-temperature stable CoSi2-S. Treatment of the surface of CoSi2 facilitates this transition and prevents the formation of pinholes. A few important parameters in the silicide reaction are shown to govern the morphology of the reacted CoSi2 layers.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-253
Abstract: Growth of epitaxial single crystal nickel and cobalt disilicide films on silicon is performed under UHV conditions by deposition of Co or Ni on silicon followed by a high temperature reaction to form the silicide. The uniformity and perfection of ultrathin epitaxial layers has been studied using transmission electron microscopy. Mechanisms controlling island growth are discussed. Island nucleation observed in pseudomorphic films of NiSi 2 /Si(100) (∼60Å thick) is shown to be the result of the difference in symmetry between the NiSi 2 and Si. Islands related by a translation vector a/4 show an equilibrium island separation of 15±1.5Å. The boundary between islands is described as a coreless defect. In comparison,, pseudomorphic layers of CoSi 2 /Si(111) are observed up to thicknesses ∼30Å. Pinholes are commonly observed in CoSi 2 /Si(111) thin films. Finite contact angles (∼50) between substrate and deposit suggest a desire for three-dimensional growth under equilibrium conditions.
Publisher: Informa UK Limited
Date: 05-1991
Publisher: Springer Science and Business Media LLC
Date: 1990
DOI: 10.1557/PROC-183-79
Abstract: Motion of ordered twin/matrix interfaces in films of silicon on sapphire occurs during high temperature annealing. This process is shown to be thermally activated and is analogous to grain boundary motion. Motion of amorphous/crystalline interfaces occurs during recrystallization of CoSi 2 and NiSi 2 from the amorphous phase. In-situ transmission electron microscopy has revealed details of the growth kinetics and interfacial roughness.
Publisher: The Electrochemical Society
Date: 03-1989
DOI: 10.1149/1.2096749
Publisher: Elsevier BV
Date: 02-1989
Publisher: AIP Publishing
Date: 05-01-1987
DOI: 10.1063/1.98264
Abstract: We have studied the process of buried oxide formation as a function of implantation and annealing conditions. Concentrating on substoichiometric implants (& ×1018 O/cm2), we varied the implantation energies from 100 keV to 1 MeV. Some apparent precipitation of SiO2 similar to that observed in Czochralski-grown silicon occurs on implantation. This means that formation of the buried oxide layer and perfection of the overlying crystalline Si layer depend more strongly on the substrate temperature during the implant than on the annealing temperature.
Publisher: American Physical Society (APS)
Date: 28-03-1988
Publisher: Cambridge University Press (CUP)
Date: 08-1986
DOI: 10.1017/S0424820100143559
Abstract: High resolution electron microscopy (HREM) is a powerful tool for the determination of interface atomic structure. With the previous generation of HREM's of point-to-point resolution (r pp ) .5Å, imaging of semiconductors in only directions was possible. Useful imaging of other important zone axes became available with the advent of high voltage, high resolution microscopes with rpp .8Å, leading to a study of the NiSi 2 interface. More recently, it was shown that images in , and directions are easily obtainable from Si in the new medium voltage electron microscopes. We report here the examination of the important Si/Si0 2 interface with the use of a JEOL 4000EX HREM with r pp .8Å, in a orientation. This represents a true structural image of this interface.
Publisher: AIP Publishing
Date: 07-12-1987
DOI: 10.1063/1.98504
Abstract: We report the fabrication of epitaxial CoSi2 layers on Si(111) as thin as 1 nm. The crystalline lattice of these layers is coherent with the Si lattice, and the silicide is electrically continuous. There are pronounced structural differences between films which are less than 3 nm thick and those which are thicker. The resistivity of the layers increases sharply with decreasing thickness. This is the first report of the growth of coherent, electrically continuous CoSi2 layers on Si.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-361
Abstract: We have explored the possibility of fabricating a metal base transistor in the Si/CoSi 2 material system. Utilizing recent advances in the growth of thin, pinhole free, CoSi 2 layers on Si(111) we have measured the transistor characteristics of a Si/CoSi 2 /Si structure. The observed low common emitter current gain is attributed to an absence of current carrying states in the CoSi 2 transistor base.
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1557/PROC-100-399
Abstract: A novel regime of crystal growth and segregation has been observed. Amorphous Si layers were uniformly doped with Au and epitaxial crystallization was induced in the temperature range 250–420°C using 2.5 MeV Ar ion irradiation. The Au segregation at the amorphous/crystal interface is analogous to behavior at liquid/solid interfaces except that the interfacial segregation coefficient of 0.007 at 320°C is independent of velocity between 0.6 and 6A/sec. This process results in the trapping of Au in crystalline Si at concentrations some ten orders of magnitude in excess of equilibrium concentration.
Publisher: Springer Science and Business Media LLC
Date: 1991
DOI: 10.1557/PROC-256-189
Abstract: The luminescent characteristics of porous silicon are affected by the preparation conditions as well as subsequent treatment. Oxidation, which easily occurs in ambient conditions under illumination, greatly reduces the luminescence efficiency. Vertical inhomogeneity, which is inherent from the preparation procedure, can complicate interpretation of results, especially following treatments which non-uniformly affect the porous material. These results point out the need to pay careful attention to the s le's structure and history, as well as the necessity of controlling this degradation in order to realize practical luminescent devices.
Publisher: Cambridge University Press (CUP)
Date: 08-1992
DOI: 10.1017/S0424820100131395
Abstract: Epitaxial reordering of amorphous Si(a-Si) on an underlying single-crystal substrate occurs well below the melt temperature by the process of solid phase epitaxial growth (SPEG). Growth of crystalline Si(c-Si) is known to be enhanced by the presence of small amounts of a metallic phase, presumably due to an interaction of the free electrons of the metal with the covalent Si bonds near the growing interface. Ion implantation of Ni was shown to lower the crystallization temperature of an a-Si thin film by approximately 200°C. Using in situ transmission electron microscopy (TEM), precipitates of NiSi 2 formed within the a-Si film during annealing, were observed to migrate, leaving a trail of epitaxial c-Si. High resolution TEM revealed an epitaxial NiSi 2 /Si(l11) interface which was Type A. We discuss here the enhanced nucleation of c-Si and subsequent silicide-mediated SPEG of Ni-implanted a-Si. Thin films of a-Si, 950 Å thick, were deposited onto Si(100) wafers capped with 1000Å of a-SiO 2 . Ion implantation produced sharply peaked Ni concentrations of 4×l0 20 and 2×l0 21 ions cm −3 , in the center of the films.
Publisher: AIP Publishing
Date: 19-12-1988
DOI: 10.1063/1.100221
Abstract: Liquid phase nonequilibrium segregation and trapping of Au in Si induced by Q-switched laser irradiation are reported. Depending on the incident laser energy density, irradiation results in either amorphization or recrystallization of a near surface layer. In the latter case, at interface velocities of 9 m/s, the segregation coefficient is 0.1±0.02 and Au is trapped in near-substitutional lattice sites at concentrations of 0.5 at. %. These results are compared with recent data on solid phase, ion beam induced segregation, where Au at the amorphous-crystal interface is trapped on nonunique lattice sites.
Publisher: AIP Publishing
Date: 11-04-1988
DOI: 10.1063/1.99161
Abstract: The radiation-enhanced diffusion of implanted Au markers in amorphous Si has been measured in the temperature range 77–693 K. S les were irradiated with 2.5 MeV Ar ions. The diffusion coefficients show three well-defined regions. For temperatures & K, diffusion is athermal and due to ballistic mixing. For temperatures in the range 400–700 K diffusion is Arrhenius-type with an activation energy of 0.37 eV and is considerably enhanced over the normal thermal diffusion. The defects that cause the enhanced diffusion come from nuclear energy loss processes. Thermal diffusion, with an activation energy of 1.42 eV, dominates at temperatures greater than 750 K.
Publisher: AIP Publishing
Date: 13-01-1992
DOI: 10.1063/1.106971
Abstract: The silicide-mediated phase transformation of amorphous to crystalline silicon was observed in situ in the transmission electron microscope. Crystallization of nickel-implanted amorphous silicon occurred at ∼500 °C. Nickel disilicide precipitates were observed to migrate through an amorphous Si film leaving a trail of crystalline Si. Growth occurred parallel to 〈111〉 directions. High resolution electron microscopy revealed an epitaxial NiSi2/Si(111) interface which was Type A. A diffusion-controlled mechanism for the enhanced crystallization rate was determined.
Publisher: Springer International Publishing
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1557/PROC-138-373
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-91-427
Abstract: We have performed electrical transport measurements on ultrathin films of epitaxial CoSi 2 on Si(111) with film thickness ranging down to ∼10A. The resistivities exhibit temperature dependences characteristic of a metal and a thickness dependence which rises steeply with decreasing thickness suggestive of a quantum size effect. At the lowest temperatures (≲ 10K) the resistivities of the thinner films increase logarithmically with inverse temperature characteristic of transport in the weak localization regime as has been confirmed by magnetoresistance measurements. Hall effect measurements establish that carrier densities (holes) in the ultrathin films are essentially identical to those in bulk CoSi 2 , i.e. 26 × 10 22 cm −3 .
Publisher: AIP Publishing
Date: 28-03-1988
DOI: 10.1063/1.99204
Abstract: Ion-beam-induced epitaxial recrystallization of Au-implanted amorphous silicon at temperatures & °C has been studied. Crystallization was induced using a 2.5 MeV Ar beam. Segregation of Au at the moving crystal/amorphous silicon interface occurs with an interface velocity of 5 Å/s. At high Au concentrations, the interface breaks down with the formation of twins. The twinned crystal/amorphous interface then propagates under further irradiation with a reduced interface velocity of 3 Å/s. Unusual Au redistribution profiles are obtained as a result of the sudden change in interface morphology. The Au profiles are interpreted on the basis of classical segregation theory with the interfacial segregation coefficient changing from 0.0012 to 0.02 at the onset of twin formation.
Publisher: Informa UK Limited
Date: 1993
Publisher: ACM
Date: 13-10-2015
Publisher: Cambridge University Press (CUP)
Date: 06-08-1989
DOI: 10.1017/S0424820100154275
Abstract: Cubic NiSi 2 grows epitaxially on Si (100) and is of interest as a Schottky contact. Metal layers on n-type Si (100) have a Schottky barrier height, ø B of 0.47 eV. Reproducibility of ø B appears dependent on the defect structure of epitaxial thin films and attention has centered on the interfacial bonding configurations. Room temperature deposition of Ni “templates” followed by reaction at ∼450°C result in flat, abrupt NiSi 2 /Si (100) interfaces. High Resolution Electron Microscopy (HREM) has revealed six-fold coordinated Ni atoms in the interfacial plane by the methods of image simulation and rigid shift displacements. The preferred bonding configuration viewed in the [011] direction is illustrated in Figure 1(a) where the arrow indicates the NiSi 2 termination leaving two dangling bonds per Ni atom. Alternatively an extra layer of Si could be inserted at the interface shown in Figure lb resulting in 8-fold coordinated Ni and 2-fold coordinated Si. If relaxation of atom positions in the interface plane occurs, in a manner analogous to reconstruction of clean surfaces or dislocation cores, additional interfacial bonding models can be proposed, Figures 1c, 1d.
Publisher: AIP Publishing
Date: 15-06-1993
DOI: 10.1063/1.353446
Abstract: The nucleation and growth of isolated nickel disilicide precipitates in Ni-implanted amorphous Si thin films and the subsequent low-temperature silicide-mediated crystallization of Si was studied using in situ transmission electron microscopy. Analysis of the spatial distribution of the NiSi2 precipitates strongly suggested the occurrence of site saturation during nucleation. NiSi2 precipitates were observed in situ to migrate through the amorphous Si thin films leaving a trail of crystalline Si at temperatures as low as ∼484 °C. Initially, a thin region of epitaxial Si formed on {111} faces of the octahedral NiSi2 precipitates with a coherent interface which was shown by high-resolution electron microscopy to be Type A. Migration of the NiSi2 precipitates led to the growth of needles of Si which were parallel to 〈111〉 directions. The growth rate of the crystalline Si was limited by diffusion through the NiSi2 precipitates, and an effective diffusivity was determined at 507 and 660 °C. A mechanism for the enhanced growth rate of crystalline Si is proposed.
Publisher: Springer Science and Business Media LLC
Date: 05-1990
Abstract: We have studied the structural and electrical properties of ultrathin cobalt silicide films deposited on Si(211) and (311) and annealed at a variety of temperatures. Transmission electron microscopy reveals two regimes of silicide growth. If more than 10 Å of Co is deposited, textured CoSi forms at low temperatures, which transforms to two epitaxial orientations of CoSi 2 at about 500°C. If less than 10 Å of Co is deposited, only one epitaxial CoSi 2 orientation is observed, which occurs in discontinuous islands or lines. The resistivities of the thinnest films reflect the degree of continuity of the silicide layers. In thicker films, where disorder is the major factor, the resistivity for intermediate annealing temperatures (∼500°C) depends dramatically on the orientation of the Si substrate, being an order of magnitude lower for Si(311) and (211) than for (111). The differences between these observations and those made on films grown under the same conditions on Si(111) can be understood by noting both the greater tendency of the film to form intermediate phases which are epitaxial on the high symmetry Si(111) surface and the faceting of the CoSi 2 -Si(311) and (211) interfaces.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-107-259
Abstract: We have explored the possibility of fabricating a metal base transistor in the Si/CoSi 2 material system. Utilizing recent advances in the growth of thin, pinhole free, CoSi 2 layers on Si(111) we have measured the transistor characteristics of a Si/CoSi 2 /Si structure. The observed low common emitter current gain is attributed to an absence of current carrying states in the CoSi 2 transistor base.
Publisher: American Physical Society (APS)
Date: 04-04-1988
Publisher: IOP Publishing
Date: 20-12-1984
DOI: 10.1088/0022-3719/17/35/017
Abstract: Results are presented of high-resolution luminescence studies from in idual dislocations and related defects in ZnSe and InP performed in a transmission electron microscope. In the case of ZnSe unusual luminescence bands (Y at 2.60 eV and S at 2.52 eV) originally observed in photoluminescence studies are attributed to dislocations. In some instances, complete quenching of the excitonic transitions was observed to correlate with the presence of Y emission from complex dislocation tangles. In the case of in idual screw dislocations this quenching of the exciton luminescence was found to be variable for ex le reduction of the exciton signal was not always observed. For InP, donor-exciton-related transitions were quenched at in idual screw dislocations. Donor-acceptor pair/free-to-bound and deep level (band C) transitions were unaffected. For the case of InP, unlike ZnSe, no dislocation-related luminescence was observed within the system detection limit (0.7-4.0 eV).
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1557/PROC-139-97
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1557/PROC-77-271
Abstract: Abrupt, epitaxial silicide/silicon heterostructures may be grown so that, for the first time, the physics of electron transport across near perfect, single crystal, metal/semiconductor interfaces may be probed experimentally. Transport measurements through type-A and -B oriented NiSi 2 layers on Si(111) substrates have revealed Schottky barrier heights differing by 140 meV. In this paper we present results of experiments designed to explore the possible role of bulk and interface defects in determining the potential barrier at these near ideal epitaxial metal-semiconductor contacts. We have found little evidence for the presence of defects and the Schottky barrier is insensitive to details of the microscopic interfacial perfection. By contrast we find that both the electrical quality and magnitude of the barrier occurring at the NiSi 2 /Si(100) heterojunction are dependent upon details of the microscopic interfacial perfection.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-107-253
Abstract: A new in-situ rapid thermal annealing (RTA) apparatus which can be used to anneal entire wafers in an ultra high vacuum environment has been designed to be used in conjunction with the epitaxial growth of heterostructures. Drastic improvement in the crystallinity of CaF 2 /Si(100) can be achieved with RTA, and our results suggest that RTA can be used as an on-line processing technique for novel epitaxial structures.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-94-151
Abstract: In-situ observations of the growth of CoSi 2 films by Co deposition in an ultrahigh vacuum transmission electron microscope are described. Results include the observation of intermediate epitaxial phases (both hexagonally distorted Co 2 Si and CoSi) and the observation that pinholes nucleate in CoSi 2 films after growth in a metastable layer mode.
Publisher: Springer Science and Business Media LLC
Date: 1991
DOI: 10.1557/PROC-91-365
Abstract: We present evidence on the types of structural changes caused by the rapid thermal annealing of two types of heteroepitaxial layers: CaF 2 /CoSi 2 /Si(111) and Si(100) on A1 2 O 3 (1102). We find that grains in a film can be merged into a single crystal and that the microtwin density can be dramatically lowered. We also find a number of changes in the structure of the heteroepitaxial interfaces.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-355
Abstract: A new in-situ rapid thermal annealing (RTA) apparatus which can be used to anneal entire wafers in an ultra high vacuum environment has been designed to be used in conjunction with the epitaxial growth of heterostructures. Drastic improvement in the crystallinity of CaF 2 /Si(100) can be achieved with RTA, and our results suggest that RTA can be used as an on-line processing technique for novel epitaxial structures.
Publisher: Springer Science and Business Media LLC
Date: 02-1989
Abstract: We have studied the dependence of the electrical and structural properties of ultrathin cobalt silicide films on the annealing temperature and deposited Co thickness. If less than 10 Å of Co is deposited, epitaxial type B CoSi 2 forms immediately. As the deposited thickness approaches 10 Å, small amounts of Co 2 Si are observed. If greater than 10 Å of Co is deposited, epitaxial Co 2 Si forms at room temperature, which proceeds either via the reaction Co 2 Si ⇉ CoSi ⇉ CoSi 2 or via Co 2 Si ⇉ CoSi 2 during annealing. In these thicker films our results suggest that the formation of type A CoSi 2 is correlated with the presence of Co 2 Si the presence of CoSi as an intermediate phase is correlated with the occurrence of type B CoSi 2 . Both film thickness and reaction temperature strongly influence the electrical transport in these films such that very high resistivities are encountered when films either become very thin or are reacted at low temperatures. In the former case the size effect is responsible whereas in the latter the transport properties are dominated by extensive atomic-scale disorder.
Publisher: Springer Science and Business Media LLC
Date: 1995
DOI: 10.1557/PROC-405-73
Abstract: We report a kinetic analysis of low-temperature NiSi 2 -mediated crystallization of amorphous Si by in situ transmission electron microscopy. The initiation of crystallization by formation of crystalline Si on buried NiSi 2 precipitates is shown to have an activation energy of 2.8±0.7eV. Crystallization of the amorphous Si via migrating precipitates of NiSi 2 occurs with an activation energy of 2.0±0.2eV. The significance of these activation energies is discussed in terms of possible atomistic mechanisms of crystalline Si initiation and subsequent growth. Amorphous Si is reported to crystallize at temperatures as low as 450°C.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-91-445
Abstract: Ultrathin epitaxial CoSi 2 films on Si(111) have been grown in ultrahigh vacuum by room temperature deposition of Co on Si(111) followed by a high temperature anneal at ~600°C. Characterization of the thin films with transmission electron microscopy has revealed pseudomorphic growth up to thicknesses ~30Å. Pinholes present in the pseudomorphic thin films are thought to prevent the trapping of dislocations within the film. A clear transition to films containing a regular network of misfit dislocations occurs at ~40Å. Evidence for the growth of CoSi 2 via intermediate metal-rich silicide phases is observed.
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1557/PROC-74-597
Abstract: The microstructure of oxygen implanted silicon for use in silicon-on- insulator technology has been examined by transmission electron microscopy. A variety of buried oxide layers prepared using oxygen doses below and above that required for stoichiometric SiO 2 formation have been studied. High resolution imaging in crosssection has revealed exceptionally flat Si-SiO 2 interfaces, comparable to the best thermally grown Si-SiO 2 interfaces. Examination of as-implanted material shows a complex interwoven crystalline/amorphous structure which evolves during high temperature (1350–1400° C) annealing into a buried oxide layer.
Publisher: Springer Science and Business Media LLC
Date: 1987
DOI: 10.1557/PROC-102-45
Abstract: High resolution electron microscopy has been used to determine the atomic structure at the epitaxial CaF 2 /Si(111) interface before and after a rapid thermal anneal. Direct Ca-Si bonding at the interface, with 8-fold coordinated Ca atoms is observed in as-grown layers. Fluorine is preferentially removed from the interface during a rapid thermal anneal leaving 5-fold coordinated Ca atoms. A dramatic improvement in the electrical properties of the interface is observed after annealing. The measured interface state density is reduced from ≳10 13 cm −2 to ≲10 11 cm −2 . This has been correlated with the removal of F from the interface. No evidence for direct F-Si bonding is observed.
Publisher: Informa UK Limited
Date: 10-1992
Publisher: Cambridge University Press (CUP)
Date: 08-1986
DOI: 10.1017/S0424820100145431
Abstract: Thin film, high purity II-VI semiconductors such as ZnSe are attracting increasing interest as optoelectronic device materials. Recent developments in low temperature epitaxial growth techniques such as organometallic chemical vapour deposition (MOCVD) have enabled growth of single crystal films on a variety of different substrates resulting in blue emission bands at 300K. Characterization of undoped, Al-doped and In-doped MOCVD ZnSe/(100)GaAs layers grown at RSRE, Malvern has been performed using transmission electron microscopy (TEM) and cathodoluminescence (CL). Optically and electrically active stacking faults and dislocations have been observed, revealing correlations with emission bands Y at 2.60eV and S at 2.52eV. Y and S are particularly characteristic of epitaxial growth and radiative emission has been observed from in idual dislocations and complex tangles of dislocations commonly found in doped ZnSe. Recent work has concentrated on obtaining an understanding of the mechanism of radiative recombination at dislocations by studying thermal activation energies and excitation dependences.
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