Recrystallization of highly-mismatched Be(x)Zn(1-x)O alloys: formation of a degenerate interface.
Recrystallization of highly-mismatched Be(x)Zn(1-x)O alloys: formation of a degenerate interface.
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DOI：
10.1021/am5043388
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发表时间：
2014-10
影响因子：
9.5
通讯作者：
Dae-Sung Park;S. K. Vasheghani Farahani;M. Walker;James J. Mudd;Haiyuan Wang;A. Krupski;E. B. Thorsteinsson;D. Seghier;Chel-Jong Choi;C. Youn;C. McConville
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文献类型：
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作者：
Dae-Sung Park;S. K. Vasheghani Farahani;M. Walker;James J. Mudd;Haiyuan Wang;A. Krupski;E. B. Thorsteinsson;D. Seghier;Chel-Jong Choi;C. Youn;C. McConville
研究了在600-950 °C退火温度范围内，生长在Al 2 O3（0001）衬底上的亚稳氧化物合金薄膜（多相Be（x）Zn（1-x）O（BZO））的热致相变效应。一个显着的结构转变一起示出的应变弛豫和原子重新分布在退火膜。增加退火温度引发的外扩散和偏析的Be和随后的成核的纳米粒子在表面上，对应于一个单调下降的晶格声子能量和带隙能量的薄膜。红外反射模拟识别出高导电性ZnO界面层（对于≥ 800 °C的退火温度，厚度在10-29 nm的范围内）。具有温度无关的载流子浓度和迁移率的高度简并界面层显著影响BZO薄膜的电子和光学性质。采用平行导电模型来确定体和界面区域的载流子浓度和电导率。的状态密度的平均有效质量的界面的传导电子计算为在0.31 m0和0.67 m0的范围内。电导率高达1.4 × 10（3）S · cm（-1），相当于界面层载流子浓度n（Int）= 2.16 × 10（20）cm（-3），与高掺杂ZnO的最高电导率相当。这种纳米级简并界面层的起源归因于Be和Zn的反扩散，从而导致Zn杂质的高积累和电荷补偿缺陷的巨大减少。这些观察结果提供了广泛的理解的热力学和相变在Be（x）Zn（1-x）O合金的高导电性和透明的氧化物为基础的设备和制造其合金纳米结构的应用。
We investigate the effect of thermally induced phase transformations on a metastable oxide alloy film, a multiphase Be(x)Zn(1-x)O (BZO), grown on Al2O3(0001) substrate for annealing temperatures in the range of 600-950 °C. A pronounced structural transition is shown together with strain relaxation and atomic redistribution in the annealed films. Increasing annealing temperature initiates out-diffusion and segregation of Be and subsequent nucleation of nanoparticles at the surface, corresponding to a monotonic decrease in the lattice phonon energies and band gap energy of the films. Infrared reflectance simulations identify a highly conductive ZnO interface layer (thicknesses in the range of ≈ 10-29 nm for annealing temperatures ≥ 800 °C). The highly degenerate interface layers with temperature-independent carrier concentration and mobility significantly influence the electronic and optical properties of the BZO films. A parallel conduction model is employed to determine the carrier concentration and conductivity of the bulk and interface regions. The density-of-states-averaged effective mass of the conduction electrons for the interfaces is calculated to be in the range of 0.31 m0 and 0.67 m0. A conductivity as high as 1.4 × 10(3) S · cm(-1) is attained, corresponding to the carrier concentration n(Int) = 2.16 × 10(20) cm(-3) at the interface layers, and comparable to the highest conductivities achieved in highly doped ZnO. The origin of such a nanoscale degenerate interface layer is attributed to the counter-diffusion of Be and Zn, rendering a high accumulation of Zn interstitials and a giant reduction of charge-compensating defects. These observations provide a broad understanding of the thermodynamics and phase transformations in Be(x)Zn(1-x)O alloys for the application of highly conductive and transparent oxide-based devices and fabrication of their alloy nanostructures.