skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Low-Temperature Surface Preparation and Epitaxial Growth of ZnS and Cu 2ZnSnS 4 on ZnS(110) and GaP(100)

Abstract

Here we give a summary of the low-temperature preparation methods of ZnS(110) and GaP(100) crystals for epitaxial growth of ZnS and Cu 2ZnSnS 4 (CZTS) via molecular beam epitaxy. Substrates were prepared for epitaxial growth by means of room-temperature aqueous surface treatments and subsequent ultra-high vacuum transfer to the deposition system. Epitaxial growth of ZnS was successful at 500 K on both ZnS(110) and GaP(100) as only single domains were observed with electron backscatter diffraction; furthermore, transmission electron microscopy measurements confirmed an epitaxial interface. Epitaxial growth of CZTS was successful on ZnS at 700 K. However, epitaxial growth was not possible on GaP at 700 K due to Ga xS y formation, which significantly degraded the quality of the GaP crystal surface. Although CZTS was grown epitaxially on ZnS, growth of multiple crystallographic domains remains a problem that could inherently limit the viability of epitaxial CZTS for model system studies.

Authors:
 [1];  [2];  [1]; ORCiD logo [1];  [1]
  1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  2. Univ. of Florida, Gainesville, FL (United States). Dept. of Chemical Engineering
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S); National Science Foundation (NSF)
OSTI Identifier:
1393378
Report Number(s):
NREL/JA-5K00-68184
Journal ID: ISSN 0022-0248
Grant/Contract Number:
AC36-08GO28308; CHE-1230929
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Crystal Growth
Additional Journal Information:
Journal Volume: 478; Journal ID: ISSN 0022-0248
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; sulfides; molecular beam epitaxy; zinc compounds; solar cells; semiconducting quaternary alloys

Citation Formats

Harvey, Steven P, Wilson, Samual, Moutinho, Helio R, Norman, Andrew, and Teeter, Glenn R. Low-Temperature Surface Preparation and Epitaxial Growth of ZnS and Cu2ZnSnS4 on ZnS(110) and GaP(100). United States: N. p., 2017. Web. doi:10.1016/j.jcrysgro.2017.08.018.
Harvey, Steven P, Wilson, Samual, Moutinho, Helio R, Norman, Andrew, & Teeter, Glenn R. Low-Temperature Surface Preparation and Epitaxial Growth of ZnS and Cu2ZnSnS4 on ZnS(110) and GaP(100). United States. doi:10.1016/j.jcrysgro.2017.08.018.
Harvey, Steven P, Wilson, Samual, Moutinho, Helio R, Norman, Andrew, and Teeter, Glenn R. 2017. "Low-Temperature Surface Preparation and Epitaxial Growth of ZnS and Cu2ZnSnS4 on ZnS(110) and GaP(100)". United States. doi:10.1016/j.jcrysgro.2017.08.018.
@article{osti_1393378,
title = {Low-Temperature Surface Preparation and Epitaxial Growth of ZnS and Cu2ZnSnS4 on ZnS(110) and GaP(100)},
author = {Harvey, Steven P and Wilson, Samual and Moutinho, Helio R and Norman, Andrew and Teeter, Glenn R},
abstractNote = {Here we give a summary of the low-temperature preparation methods of ZnS(110) and GaP(100) crystals for epitaxial growth of ZnS and Cu2ZnSnS4 (CZTS) via molecular beam epitaxy. Substrates were prepared for epitaxial growth by means of room-temperature aqueous surface treatments and subsequent ultra-high vacuum transfer to the deposition system. Epitaxial growth of ZnS was successful at 500 K on both ZnS(110) and GaP(100) as only single domains were observed with electron backscatter diffraction; furthermore, transmission electron microscopy measurements confirmed an epitaxial interface. Epitaxial growth of CZTS was successful on ZnS at 700 K. However, epitaxial growth was not possible on GaP at 700 K due to GaxSy formation, which significantly degraded the quality of the GaP crystal surface. Although CZTS was grown epitaxially on ZnS, growth of multiple crystallographic domains remains a problem that could inherently limit the viability of epitaxial CZTS for model system studies.},
doi = {10.1016/j.jcrysgro.2017.08.018},
journal = {Journal of Crystal Growth},
number = ,
volume = 478,
place = {United States},
year = 2017,
month = 8
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on August 12, 2018
Publisher's Version of Record

Save / Share:
  • The evolution of surface roughness on epitaxial Si films grown at 300{degree}C by ultrahigh vacuum ion-beam sputter deposition onto nominally singular, [100]-, and [110]-miscut Si(001) is inconsistent with conventional scaling and hyperscaling laws for kinetic roughening. Unstable growth leading to the formation of mounds separated by a well-defined length scale is observed on all substrates. Contrary to previous high-temperature growth results, the presence of steps during deposition at 300{degree}C increases the tendency toward unstable growth resulting in a much earlier development of mound structures and larger surface roughness on vicinal substrates. {copyright} {ital 1996 The American Physical Society.}
  • Evolution of surface roughness in epitaxial Si{sub 0.7}Ge{sub 0.3} alloys grown on Si(001) as a function of temperature (200-600 C), thickness ({ital t}=7.5-100 nm), and substrate miscut were investigated by atomic force microscopy and quantified in terms of the height-difference correlation function {ital G}({rho}), in which {rho} is lateral distance and [{ital G}({rho}{r_arrow}{infinity})]{sup 1/2} is proportional to the surface width. The films were deposited by ultrahigh vacuum ion-beam sputter deposition at 0.1 nms{sup {minus}1}. Strain-induced surface roughening was found to dominate in alloys grown on singular Si(001) substrates at {ital T}{sub {ital s}}{approx_gt}450{degree}C where [{ital G}({rho}{r_arrow}{infinity})]{sup 1/2} initially increases withmore » increasing {ital t} through the formation of coherent islanding. The islands are preferentially bounded along {l_angle}100{r_angle} directions and exhibit 105 faceting. This tendency is enhanced, with much better developed {l_angle}100{r_angle} islands separated by deep trenches{emdash}of interest for growth of self-assembled nanostructures{emdash}in films grown on Si(001)-4{degree}[100]. Increasing the film thickness above critical values for strain relaxation leads to island coalescence and surface smoothening. At very low growth temperatures ({ital T}{sub {ital s}}{le}250{degree}C), film surfaces roughen kinetically, due to limited adatom diffusivity, but at far lower rates than in the higher-temperature strain-induced regime. Si{sub 0.7}Ge{sub 0.3} alloy surfaces are smoother, while the films exhibit larger critical epitaxial thicknesses, than those of pure Si films grown in this temperature regime. There is an intermediate growth temperature range, however, over which the alloy film surfaces remain extremely smooth even at thicknesses near critical values for strain relaxation. This latter result is of potential importance for device fabrication. {copyright} {ital 1996 American Institute of Physics.}« less
  • Fully strained single-crystal metastable Ge{sub 1-x}Sn{sub x} layers were grown on Ge(001) in order to probe the role of Sn dopant and alloy concentrations (C{sub Sn}=1x10{sup 18} cm{sup -3} to 6.1 at. %) on surface roughening pathways leading to epitaxial breakdown during low-temperature (155 deg. C) molecular-beam epitaxy of compressively strained films. The addition of Sn was found to mediate Ge(001) surface morphological evolution through two competing pathways. At very low Sn concentrations (x < or approx. 0.02), the dominant effect is a Sn-induced enhancement in both the Ge surface diffusivity and the probability of interlayer mass transport. This, inmore » turn, results in more efficient filling of interisland trenches, and thus delays epitaxial breakdown. In fact, breakdown is not observed at all for Sn concentrations in the doping regime, 1x10{sup 18}{<=}C{sub Sn}<4.4x10{sup 20} cm{sup -3} (2.3x10{sup -5}{<=}x<0.010){exclamation_point} At higher concentrations, there is a change in Ge{sub 1-x}Sn{sub x}(001) growth kinetics due to a rapid increase in the amount of compressive strain. This leads to a gradual reduction in the film thickness h{sub 1}(x) corresponding to the onset of breakdown as strain-induced roughening overcomes the surface smoothening effects, and results in an increase in the overall roughening rate. We show that by varying the Sn concentration through the dopant to dilute alloy concentration range during low-temperature Ge(001) growth, we can controllably manipulate the surface roughening pathway, and hence the epitaxial thickness, over a very wide range.« less
  • Cited by 6
  • To explore the possibility of Cu{sub 2}ZnSnS{sub 4} (CZTS)/Si based tandem solar cells, the heteroepitaxy of tetragonal Cu{sub 2}ZnSnS{sub 4} thin films on single crystalline cubic Si (111) wafers with 4° miscut is obtained by molecular beam epitaxy. The X-ray θ-2θ scan and selected area diffraction patterns of the CZTS thin films and Si substrates, and the high resolution transmission electron microscopy image of the CZTS/Si interface region demonstrate that the CZTS thin films are epitaxially grown on the Si substrates. A CZTS/Si P-N junction is formed and shows photovoltaic responses, indicating the promising application of epitaxial CZTS thin filmsmore » on Si.« less