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Title: Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon

Abstract

Epitaxial silicon thin film growth has been achieved on crystalline silicon substrates using aluminum induced crystallization of amorphous silicon. The phenomenon of layer inversion has been utilized in this process. Silicon wafers <100> were used as the starting crystalline structure for the grown films. After the wafer is cleaned a thin layer of aluminum (300 nm) was deposited by sputtering. This deposition was followed by 300 nm film of amorphous silicon deposited using plasma enhanced chemical vapor deposition method. After annealing the samples for 40 minutes at 525 C, a continuous film of silicon was formed on the silicon substrate. X-ray diffraction spectrum indicated that this film has the same orientation as that of the substrate. Scanning electron microscopy cross section images showed indistinguishable interface between the substrate and the crystallized film. Cross sectional transmission electron microscopy studies of the crystallized structure showed epitaxial nature of the films.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
944486
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Amorphous and Polycrystalline Thin-Film Silicon Science and Technology: Proceedings of the Materials Research Society Symposium, 18-21 April 2006, San Francisco, California; Materials Research Society Symposium Proceedings, Vol. 910; Related Information: Paper No. 0910-A21-04
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ALUMINIUM; ANNEALING; CHEMICAL VAPOR DEPOSITION; CROSS SECTIONS; CRYSTALLIZATION; DEPOSITION; ORIENTATION; SCANNING ELECTRON MICROSCOPY; SILICON; SPUTTERING; SUBSTRATES; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; Solar Energy - Photovoltaics

Citation Formats

Sharif, K., Abu-Safe, H. H., Naseem, H. A., Brown, W. D., Al-Jassim, M., and Kishore, R. Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon. United States: N. p., 2006. Web.
Sharif, K., Abu-Safe, H. H., Naseem, H. A., Brown, W. D., Al-Jassim, M., & Kishore, R. Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon. United States.
Sharif, K., Abu-Safe, H. H., Naseem, H. A., Brown, W. D., Al-Jassim, M., and Kishore, R. Sun . "Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon". United States. doi:.
@article{osti_944486,
title = {Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon},
author = {Sharif, K. and Abu-Safe, H. H. and Naseem, H. A. and Brown, W. D. and Al-Jassim, M. and Kishore, R.},
abstractNote = {Epitaxial silicon thin film growth has been achieved on crystalline silicon substrates using aluminum induced crystallization of amorphous silicon. The phenomenon of layer inversion has been utilized in this process. Silicon wafers <100> were used as the starting crystalline structure for the grown films. After the wafer is cleaned a thin layer of aluminum (300 nm) was deposited by sputtering. This deposition was followed by 300 nm film of amorphous silicon deposited using plasma enhanced chemical vapor deposition method. After annealing the samples for 40 minutes at 525 C, a continuous film of silicon was formed on the silicon substrate. X-ray diffraction spectrum indicated that this film has the same orientation as that of the substrate. Scanning electron microscopy cross section images showed indistinguishable interface between the substrate and the crystallized film. Cross sectional transmission electron microscopy studies of the crystallized structure showed epitaxial nature of the films.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
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  • Aluminum-induced crystallization of hydrogenated amorphous silicon was used to fabricate epitaxial silicon films through solid phase epitaxy. Silicon wafers of (100) orientation were used as the starting crystalline structure for the epitaxial thin film growth. A configuration of c-Si/Al/a-Si:H was used to produce these films through the phenomenon of layer inversion. A thin layer of aluminum (300 nm) was deposited on a silicon wafer by sputtering. On top of this layer, a 300 nm amorphous silicon film was deposited using plasma-enhanced chemical vapor deposition. After annealing the samples at 475 C for 40minutes, a continuous film of crystalline silicon wasmore » formed on the silicon substrate. X-ray diffraction, scanning electron microscopy, and cross- sectional transmission electron microscopy were used to characterize the films. Auger depth profiling indicated the formation of a Si/Al mixed phase within the first few minutes of annealing.« less
  • Poly-crystalline silicon (poly-Si) thin films have been prepared by aluminum induced crystallization (AiC) technique. Hydrogenated amorphous silicon (a-Si:H) thin films were prepared by sputtering a silicon target in hydrogen and argon ambient. It was observed that deposition rates increased more than two folds with the introduction of the hydrogen in the deposition chamber. The a-Si:H thin films were coated with a thin layer of sputtered aluminum (AI). X-ray diffraction (XRD) confirmed that the crystallization commenced at as low as 225 C. The depth profile of the annealed samples, obtained by scanning Auger microscopy (SAM), did not show any layer exchangemore » below 300 C. The SAM analysis showed clear layer exchange in the higher temperature ( >350 C) region.« less
  • A metal-induced crystallization (MIC) technique was used to produce large-grain poly-crystalline silicon. Two sets of samples were prepared by first sputtering Al onto glass substrates. For one set of samples, hydrogenated amorphous silicon (a-Si:H) was sputtered on top of the Al without breaking the vacuum. For the second set, the samples were taken out of the vacuum chamber and exposed to the atmosphere to grow a very thin layer of native aluminum oxide before sputter depositing the a-Si:H. Both sets of samples were then annealed at temperatures between 400 and 525C for 40 min. X-ray diffraction patterns confirmed the crystallizationmore » of the samples. Scanning Auger microanalysis was used to confirm that the a-Si:H and Al layers exchanged positions in this structure during the crystallization process. Auger mapping revealed the formation of large grain poly-silicon (10-20 m). A model is proposed to explain how the crystallization process progresses with anneal temperature.« less
  • The crystallization properties of amorphous silicon (a-Si) thin film deposited by rf magnetron sputter deposition with substrate bias have been thoroughly characterized. The crystallization kinetics for films deposited with substrate bias is enhanced relative to unbiased a-Si by films. The enhanced crystallization for substrate biased a-Si films are attributed to ion enhanced nucleation of crystallites during sputter deposition which subsequently grow during the postdeposition anneal. Conversely films sputter deposited without substrate bias have more intrinsic defects and residual oxygen which enhance nucleation and retard growth, respectively, and lead to a large number of small crystallites.