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Title: Real-Time Synchrotron X-ray Studies of Low- and High-temperature Nitridation of c-plane Sapphire

Abstract

The plasma nitridation kinetics of c-plane sapphire at both low (200-300 {sup o}C) and high (750 {sup o}C) substrate temperatures was examined using grazing-incidence real-time x-ray diffraction, in situ x-ray reflection and in situ reflection high-energy electron diffraction (RHEED). These monitored the evolution of the nitride thickness, strain, and surface structure during nitridation. The evolution of the AlN(101{bar 0}) peak showed that the heteroepitaxial strain in the first layer of nitride is already significantly relaxed relative to the substrate. Subsequent layers grow with increasing relaxation. In both the high- and low-temperature nitridation cases, the results suggest that the early stage nitridation is governed by a complex nucleation and growth process. Nitridation at both temperatures apparently proceeds in a two-dimensional growth mode with the initial nucleating islands consisting of several monolayers which grow laterally. At low temperature the growth slows or even stops after impingement of the nucleating islands covering the surface, possibly due to low diffusivities through the existing layer. Initial formation and growth rates of nucleating islands at high temperatures are comparable to those at low temperatures, but subsequent growth into the substrate is significantly enhanced over the low temperature case, consistent with activation energies of 0.1-0.25 eV.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930605
Report Number(s):
BNL-80911-2008-JA
Journal ID: ISSN 1098-0121; TRN: US0901417
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B: Condensed Matter and Materials Physics; Journal Volume: 74
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACTIVATION ENERGY; ELECTRON DIFFRACTION; GRAZING INCIDENCE TOMOGRAPHY; IMPINGEMENT; KINETICS; NITRIDATION; NITRIDES; NUCLEATION; PLASMA; REFLECTION; RELAXATION; SAPPHIRE; STRAINS; SUBSTRATES; SYNCHROTRON RADIATION; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0400-1000 K; THICKNESS; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Wang,Y., Ozcan, A., Ozaydin, G., Ludwig, Jr., K., Bhattacharyya, A., Moustakas, T., Zhou, H., Headrick, R., and Siddons, P. Real-Time Synchrotron X-ray Studies of Low- and High-temperature Nitridation of c-plane Sapphire. United States: N. p., 2006. Web. doi:10.1103/PhysRevB.74.235304.
Wang,Y., Ozcan, A., Ozaydin, G., Ludwig, Jr., K., Bhattacharyya, A., Moustakas, T., Zhou, H., Headrick, R., & Siddons, P. Real-Time Synchrotron X-ray Studies of Low- and High-temperature Nitridation of c-plane Sapphire. United States. doi:10.1103/PhysRevB.74.235304.
Wang,Y., Ozcan, A., Ozaydin, G., Ludwig, Jr., K., Bhattacharyya, A., Moustakas, T., Zhou, H., Headrick, R., and Siddons, P. Sun . "Real-Time Synchrotron X-ray Studies of Low- and High-temperature Nitridation of c-plane Sapphire". United States. doi:10.1103/PhysRevB.74.235304.
@article{osti_930605,
title = {Real-Time Synchrotron X-ray Studies of Low- and High-temperature Nitridation of c-plane Sapphire},
author = {Wang,Y. and Ozcan, A. and Ozaydin, G. and Ludwig, Jr., K. and Bhattacharyya, A. and Moustakas, T. and Zhou, H. and Headrick, R. and Siddons, P.},
abstractNote = {The plasma nitridation kinetics of c-plane sapphire at both low (200-300 {sup o}C) and high (750 {sup o}C) substrate temperatures was examined using grazing-incidence real-time x-ray diffraction, in situ x-ray reflection and in situ reflection high-energy electron diffraction (RHEED). These monitored the evolution of the nitride thickness, strain, and surface structure during nitridation. The evolution of the AlN(101{bar 0}) peak showed that the heteroepitaxial strain in the first layer of nitride is already significantly relaxed relative to the substrate. Subsequent layers grow with increasing relaxation. In both the high- and low-temperature nitridation cases, the results suggest that the early stage nitridation is governed by a complex nucleation and growth process. Nitridation at both temperatures apparently proceeds in a two-dimensional growth mode with the initial nucleating islands consisting of several monolayers which grow laterally. At low temperature the growth slows or even stops after impingement of the nucleating islands covering the surface, possibly due to low diffusivities through the existing layer. Initial formation and growth rates of nucleating islands at high temperatures are comparable to those at low temperatures, but subsequent growth into the substrate is significantly enhanced over the low temperature case, consistent with activation energies of 0.1-0.25 eV.},
doi = {10.1103/PhysRevB.74.235304},
journal = {Physical Review B: Condensed Matter and Materials Physics},
number = ,
volume = 74,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The plasma nitridation kinetics of c-plane sapphire at both low (200-300 deg. C) and high (750 deg. C) substrate temperatures was examined using grazing-incidence real-time x-ray diffraction, in situ x-ray reflection and in situ reflection high-energy electron diffraction (RHEED). These monitored the evolution of the nitride thickness, strain, and surface structure during nitridation. The evolution of the AlN(1010) peak showed that the heteroepitaxial strain in the first layer of nitride is already significantly relaxed relative to the substrate. Subsequent layers grow with increasing relaxation. In both the high- and low-temperature nitridation cases, the results suggest that the early stage nitridationmore » is governed by a complex nucleation and growth process. Nitridation at both temperatures apparently proceeds in a two-dimensional growth mode with the initial nucleating islands consisting of several monolayers which grow laterally. At low temperature the growth slows or even stops after impingement of the nucleating islands covering the surface, possibly due to low diffusivities through the existing layer. Initial formation and growth rates of nucleating islands at high temperatures are comparable to those at low temperatures, but subsequent growth into the substrate is significantly enhanced over the low temperature case, consistent with activation energies of 0.1-0.25 eV.« less
  • Non-polar orientations of III-nitride semiconductors have attracted significant interest due to their potential application in optoelectronic devices with enhanced efficiency. Using in-situ surface x-ray scattering during metal-organic vapor phase epitaxy (MOVPE) of GaN on non-polar (m-plane) and polar (c-plane) orientations of single crystal substrates, we have observed the homoepitaxial growth modes as a function of temperature and growth rate. On the m-plane surface we observe all three growth modes (step-flow, layer-by-layer, and three-dimensional) as conditions are varied. In contrast, the +c-plane surface exhibits a direct cross over between step-flow and 3-D growth, with no layer-by-layer regime. The apparent activation energymore » of 2.8 ┬▒ 0.2 eV observed for the growth rate at the layer-by-layer to step-flow boundary on the m-plane surface is consistent with those observed for MOVPE growth of other III-V compounds, indicating a large critical nucleus size for islands.« less
  • Gallium adsorption and desorption on c-plane sapphire has been studied by real-time grazing incidence small-angle x-ray scattering and x-ray fluorescence as a function of substrate temperature (680-740 deg. C) and Ga flux. The x-ray techniques monitor the surface morphology evolution and amount of Ga on the surface. During deposition, nanodroplets of liquid Ga are observed to form on the surface and coarsen. The growth of droplet size during continuous deposition follows dynamical scaling, in agreement with expectations from theory and simulations which include deposition-induced droplet coalescence. However, observation of continued droplet distance scale coarsening during desorption points to the necessitymore » of including further physical processes in the modeling. The desorption rate at different substrate temperatures gives the activation energy of Ga desorption as 2.7 eV, comparable to measured activation energies for desorption from Ga droplets on other substrates and to the Ga heat of vaporization.« less