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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 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 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:
; ;  [1];  [2]; ;  [3]; ;  [4];  [5]
  1. Physics Department, Boston University, Boston, Massachusetts 02215 (United States)
  2. Department of Aerospace and Mechanical Engineering, Boston University, Boston, Massachusetts 02215 (United States)
  3. Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States)
  4. Department of Physics, University of Vermont, Burlington, Vermont 05405 (United States)
  5. National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)
Publication Date:
OSTI Identifier:
20853973
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 74; Journal Issue: 23; Other Information: DOI: 10.1103/PhysRevB.74.235304; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTIVATION ENERGY; ALUMINIUM NITRIDES; DIFFUSION; ELECTRON DIFFRACTION; EPITAXY; EV RANGE; EVOLUTION; KINETICS; LAYERS; NITRIDATION; NUCLEATION; PLASMA; REFLECTION; RELAXATION; SAPPHIRE; SEMICONDUCTOR MATERIALS; STRAINS; SUBSTRATES; SURFACES; TEMPERATURE DEPENDENCE; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Wang Yiyi, Oezcan, Ahmet S., Ludwig, Karl F. Jr., Oezaydin, Goezde, Bhattacharyya, Anirban, Moustakas, Theodore D., Zhou, Hua, Headrick, Randall L., and Siddons, D. Peter. 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 Yiyi, Oezcan, Ahmet S., Ludwig, Karl F. Jr., Oezaydin, Goezde, Bhattacharyya, Anirban, Moustakas, Theodore D., Zhou, Hua, Headrick, Randall L., & Siddons, D. Peter. 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 Yiyi, Oezcan, Ahmet S., Ludwig, Karl F. Jr., Oezaydin, Goezde, Bhattacharyya, Anirban, Moustakas, Theodore D., Zhou, Hua, Headrick, Randall L., and Siddons, D. Peter. Fri . "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_20853973,
title = {Real-time synchrotron x-ray studies of low- and high-temperature nitridation of c-plane sapphire},
author = {Wang Yiyi and Oezcan, Ahmet S. and Ludwig, Karl F. Jr. and Oezaydin, Goezde and Bhattacharyya, Anirban and Moustakas, Theodore D. and Zhou, Hua and Headrick, Randall L. and Siddons, D. Peter},
abstractNote = {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 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 = 23,
volume = 74,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • 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 stagemore » 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.« 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