ORCID Profile
0000-0002-9807-8433
Current Organisation
Australian National University
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Publisher: AIP Publishing
Date: 11-06-2018
DOI: 10.1063/1.5029346
Abstract: This letter reports on effective surface passivation of n-type crystalline silicon by ultrathin niobium oxide (Nb2O5) films prepared by atomic layer deposition (ALD) and subjected to a forming gas anneal at 300 °C. A ch ion recombination parameter J0 of 20 fA/cm2 and a surface recombination velocity Seff of 4.8 cm/s have been achieved for ultrathin films of 1 nm. The surface pretreatment was found to have a strong impact on the passivation. Good passivation can be achieved on both HF-treated c-Si surfaces and c-Si surfaces with a wet-chemically grown interfacial silicon oxide layer. On HF-treated surfaces, a minimum film thickness of 3 nm is required to achieve a high level of surface passivation, whereas the use of a wet chemically-grown interfacial oxide enables excellent passivation even for Nb2O5 films of only 1 nm. This discrepancy in passivation between both surface types is attributed to differences in the formation and stoichiometry of interfacial silicon oxide, resulting in different levels of chemical passivation. On both surface types, the high level of passivation of ALD Nb2O5 is aided by field-effect passivation originating from a high fixed negative charge density of 1–2 × 1012 cm−3. Furthermore, it is demonstrated that the passivation level provided by 1 nm of Nb2O5 can be further enhanced through light-soaking. Finally, initial explorations show that a low contact resistivity can be obtained using Nb2O5-based contacts. Together, these properties make ALD Nb2O5 a highly interesting building block for high-efficiency c-Si solar cells.
Publisher: American Chemical Society (ACS)
Date: 16-08-2018
Publisher: American Vacuum Society
Date: 02-02-2023
DOI: 10.1116/6.0002238
Abstract: Cu2O is an important p-type semiconductor material with applications in thin-film transistors, photovoltaics, and water splitting. For such applications, pinhole-free and uniform thin films are desirable, thus making atomic layer deposition (ALD) the ideal fabrication technique. However, existing ALD Cu precursors suffer from various problems, including limited thermal stability, fluorination, or narrow temperature windows. Additionally, some processes result in CuO films instead of Cu2O. Therefore, it is important to explore alternative precursors and processes for ALD of Cu2O thin films. In this work, we report the successful deposition of Cu2O using copper acetylacetonate as a precursor and a combination of water and oxygen as reactants at 200 °C. Saturation of the deposition rate with precursor and reactant dose time was observed, indicating self-limiting behavior, with a saturated growth-per-cycle of 0.07 Å. The Cu2O film was polycrystalline and uniform (RMS roughness ∼2 nm), with a direct forbidden bandgap of 2.07 eV and a direct allowed bandgap of 2.60 eV.
Publisher: American Chemical Society (ACS)
Date: 12-07-2022
Abstract: Electrochemical techniques offer great opportunities for the capture of chemical and biological entities from complex mixtures and their subsequent release into clean buffers for analysis. Such methods are clean, robust, rapid, and compatible with a wide range of biological fluids. Here, we designed an electrochemically addressable system, based on a conducting terpolymer [P(EDOT
Publisher: AIP Publishing
Date: 10-03-2017
DOI: 10.1063/1.4977200
Abstract: It is shown that previously proposed expressions for the semiconductor electron-hole product, which purport to separate the influence of carrier degeneracy and bandgap narrowing, fail to properly delineate these effects. A reformulation of the expression in which the two effects are successfully separated is proposed, valid when the majority carrier concentration is independent of bandgap narrowing, as occurs in the common case of low injection and quasi-neutrality. It is shown that under other conditions, the two effects may not be treated in isolation but that only their combined effect or the marginal effect of one or the other on the total electron-hole product may be assessed. Convenient expressions are provided for the latter case. The revised expression provides both conceptual and computational advantages for semiconductor device modelling.
Publisher: American Chemical Society (ACS)
Date: 21-09-2023
Publisher: American Chemical Society (ACS)
Date: 11-09-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2019
Publisher: Elsevier BV
Date: 03-2023
Publisher: American Chemical Society (ACS)
Date: 12-10-2021
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 2022
Publisher: AIP Publishing
Date: 14-05-2018
DOI: 10.1063/1.5029460
Abstract: Thin-film stacks of phosphorus oxide (POx) and aluminium oxide (Al2O3) are shown to provide highly effective passivation of crystalline silicon (c-Si) surfaces. Surface recombination velocities as low as 1.7 cm s−1 and saturation current densities J0s as low as 3.3 fA cm−2 are obtained on n-type (100) c-Si surfaces passivated by 6 nm/14 nm thick POx/Al2O3 stacks deposited in an atomic layer deposition system and annealed at 450 °C. This excellent passivation can be attributed in part to an unusually large positive fixed charge density of up to 4.7 × 1012 cm−2, which makes such stacks especially suitable for passivation of n-type Si surfaces.
Publisher: AIP Publishing
Date: 05-10-2021
DOI: 10.1063/5.0064808
Abstract: Surface passivation of germanium is vital for optimal performance of Ge based optoelectronic devices especially considering their rapidly increasing surface-to-volume ratios. In this work, we have investigated the surface passivation of Ge by a stack consisting of a thin layer of hydrogenated amorphous silicon (a-Si:H) and an aluminum oxide (Al2O3) capping layer. Plasma-enhanced chemical vapor deposition was used to deposit the a-Si:H (0–10 nm), while thermal and plasma-enhanced atomic layer deposition (ALD) were employed for the Al2O3 films (0–22 nm). Transient photoconductance decay measurements revealed a recombination velocity as low as 2.7 cm s−1 for an a-Si:H layer as thin as 1.8 nm and an Al2O3 film of only ∼6 nm. In this state-of-the-art passivation scheme, the plasma-enhanced ALD process for the Al2O3 capping layer proved superior to the thermal ALD process since it resulted in an exceptionally high negative fixed charge density (Qf ∼ 1013 cm−2), which proved a key factor for the low surface recombination velocity. Transmission electron microscopy and energy x-ray dispersion revealed that a thin SiOx layer (∼1.4 nm) forms between a-Si:H and Al2O3 during the ALD process, which is thought to be the origin of this high negative fixed charge density. This passivation stack is regarded as highly interesting for applications such as solar cells, nanolasers, and nano-LEDs based on p-type Ge.
Publisher: Wiley
Date: 07-04-2023
Abstract: Passivating contact technologies are essential for fabricating high‐efficiency crystalline silicon (c‐Si) solar cells, and their application and incorporation into manufacturing lines has ranked as a hot topic of research. Generally, ideal passivating contacts should combine excellent electrical contact, outstanding surface passivation, and high optical transparency. However, addressing all these criteria concurrently is challenging since it is unlikely for any single material to exhibit both efficient carrier transport and surface‐defect passivation while demonstrating negligible parasitic absorption. In this work, several earth‐abundant, wide‐bandgap materials are combined to engineer high‐quality transparent electron‐selective passivating contact structures capable of overcoming these obstacles. A highly transparent Al y TiO x /ZnO/TiO 2 stack with a total thickness of 3 nm, prepared by atomic layer deposition, is shown to provide a close‐to‐ideal passivating contact to Si surfaces by enabling dual functions of remarkable silicon surface passivation (with an effective minority carrier lifetime of 12.3 ms, an implied open‐circuit voltage of 730 mV, and a surface recombination current density prefactor of 2.6 fA cm −2 ), combined with efficient carrier transport with a very low contact resistivity of 3.4 mΩ cm 2 . These results demonstrate that low‐cost silicon interface‐engineering strategiesbased on transition metal oxides can push c‐Si solar cell performance to its theoretical limits.
No related grants have been discovered for Lachlan Black.