Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

Ji, Xiaoyu; Cheng, Hiu Yan; Grede, Alex J.; Molina, Alex; Talreja, Disha; Mohney, Suzanne E.; Giebink, Noel C.; Badding, John V.; Gopalan, Venkatraman

doi:10.1063/1.5020814

Cited by 12 publications

(8 citation statements)

References 41 publications

(48 reference statements)

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“…3 d could prove useful for optimizing the mass fabrication of films that have just reached their (predictable) invariant roughness/smoothness level, which may be applicable in solar cell manufacturing that requires such mass production of uniform wafers. In addition, as discussed in the final paragraph of the introduction, this relationship may be useful in the uniform mass coating and construction of nanostructures with a desired surface smoothness 18 .…”

Section: Resultsmentioning

confidence: 99%

“…The increased deposition rate associated with these pressures assists in rapid production, and the smoothness of the resulting films may be key in producing the high-quality films needed to make low-cost hydrogenated amorphous silicon solar cells 12 . In addition, extreme pressure depositions are one proposed method of applying a conformal coating to the interiors of nano-architectures, which would prove very advantageous to the fabrication of complex nanostructures 18 .…”

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confidence: 99%

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Growth front smoothing effects in extremely high pressure vapor deposition

Pittman

2020

Sci Rep

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Recent experimental chemical vapor depositions of silicon at extreme pressures of ~ 50 MPa (~ 500 atm) have been observed to generate remarkably smooth surfaces not predicted by lowpressure deposition models. In this paper, we propose an anti-shadowing mechanism where the collision of particles within the valleys of the surface growth front leads to smoothening. We conduct Monte Carlo simulations to simulate the evolution of film roughness at pressures between 1 and 50 MPa. We observe that surface roughness approaches an asymptotic invariant value that follows power law behavior as a function of pressure. The film thickness at which invariance begins is shown to have a similar power law behavior with respect to pressure. Our simulated results compare favorably with recent experimental observations and provide insight into the fundamental mechanisms underlying film evolution at pressures between one and hundreds of atmospheres.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Growth front smoothing effects in extremely high pressure vapor deposition

Pittman

2020

Sci Rep

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“…These sp 3 d 2 hybridized Si and Ge centers were explored for trigonal bipyramidal (TBP) geometries. Structures comprised of pentacoordinated Si and Ge were found to be the unstable in the square bipyramidal geometries and these structures favored prismane geometries (Pri) that were instead comprised of sp 3 -hybridized Si and Ge atoms. These SBP structures comprised of pentacoordinated Si and Ge centers were unstable, i.e., all structures were found to be higher-order saddle points on the potential energy hypersurface comprised of imaginary vibrational frequencies.…”

Section: ( )mentioning

confidence: 99%

Tuning Hydrogenated Silicon, Germanium, and SiGe Nanocluster Properties Using Theoretical Calculations and a Machine Learning Approach

Choi

Adamczyk

2018

J. Phys. Chem. A

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There are limited studies available that predict the properties of hydrogenated silicon–germanium (SiGe) clusters. For this purpose, we conducted a computational study of 46 hydrogenated SiGe clusters (Si x Ge y H z , 1 < X + Y ≤ 6) to predict the structural, thermochemical, and electronic properties. The optimized geometries of the Si x Ge y H z clusters were investigated using quantum chemical calculations and statistical thermodynamics. The clusters contained 6 to 9 fused Si–Si, Ge–Ge, or Si–Ge bonds, i.e., bonds participating in more than one 3- to 4-membered rings, and different degrees of hydrogenation, i.e., the ratio of hydrogen to Si/Ge atoms varied depending on cluster size and degree of multifunctionality. Our studies have established trends in standard enthalpy of formation, standard entropy, and constant pressure heat capacity as a function of cluster composition and structure. A novel bond additivity correction model for SiGe chemistry was regressed from experimental data on seven acyclic Si/Ge/SiGe species to improve the accuracy of the standard enthalpy of formation predictions. Electronic properties were investigated by analysis of the HOMO–LUMO energy gap to study the effect of elemental composition on the electronic stability of Si x Ge y H z clusters. These properties will be discussed in the context of tailored nanomaterials design and generalized using a machine learning approach.

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“…Conformal growth during deposition of thin films onto rough substrates is a relevant field of study in photovoltaics (Palomares et al, 2003;Garnett et al, 2011;Ji et al, 2018), microelectronics (Schmitz, 2018;Gowda et al, 2011), astronomy (Spiller et al, 1999;Canestrari et al, 2006;Moore et al, 2016;Stefanov et al, 2020) and biomedicine (Freitas, 2003). Recently, in orthopaedics (Marchiori et al, 2016), the increasing demand for surface functionalisation of prosthetic devices has also highlighted new areas of application of this issue.…”

Section: Introductionmentioning

confidence: 99%

Assessing conformal thin film growth under nonstochastic deposition conditions: application of a phenomenological model of roughness replication to synthetic topographic images

Bontempi

Visani

Benini

et al. 2020

Journal of Microscopy

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In this work, a simple method to follow the evolution of the surface of thin films during growth on substrates characterised by high roughness is detailed. To account for real cases as much as possible, the approach presented is based on the hypothesis that deposition takes place under nonstochastic conditions, such as those typical of many thin film processes in industry and technology. In this context, previous models for roughness replication, which are mainly based on idealised deposition conditions, cannot be applied and thus ad hoc approaches are required for achieving quantitative predictions. Here it is suggested that under nonstochastic conditions a phenomenological relation can be proposed, mainly based on local roughening of surface, to monitor the statistical similarity between the film and the substrate during growth or, in other words, to detect changes of the bare substrate morphological profile occurring during the film growth on top. Such approximation is based on surface representation in terms of power spectral density of surface heights, derived from topographic images; in this work, such method will be tested on two separate batches of synthetic images which simulate thin films growth onto a real rough substrate. In particular, two growth models will be implemented: the first reproduces the surface profile obtained during an atomic force microscopy measurement by using a simple geometrical envelope of surface, regardless the thin film growth mechanism; the second reproduces the columnar growth expected under nonstochastic deposition conditions. It will be shown that the approach introduced is capable to highlight differences between the two batches and, in the second case, to quantitatively account for the replication of the substrate roughness during growth. The

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Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

Cited by 12 publications

References 41 publications

Growth front smoothing effects in extremely high pressure vapor deposition

Growth front smoothing effects in extremely high pressure vapor deposition

Tuning Hydrogenated Silicon, Germanium, and SiGe Nanocluster Properties Using Theoretical Calculations and a Machine Learning Approach

Assessing conformal thin film growth under nonstochastic deposition conditions: application of a phenomenological model of roughness replication to synthetic topographic images

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