PRESSURE-ENHANCED CRYSTALLIZATION KINETICS OF AMORPHOUS SI AND GE - IMPLICATIONS FOR POINT-DEFECT MECHANISMS
PRESSURE-ENHANCED CRYSTALLIZATION KINETICS OF AMORPHOUS SI AND GE - IMPLICATIONS FOR POINT-DEFECT MECHANISMS
复制标题
DOI：
10.1063/1.350243
复制
发表时间：
1991-11-15
影响因子：
3.2
通讯作者：
AZIZ, MJ
中科院分区：
文献类型：
--
作者：
LU, GQ;NYGREN, E;AZIZ, MJ
报道了静水压力对本态Ge（100）和未掺杂、掺杂Si（100）固相外延生长速率的影响。样品在高温高压金刚石砧槽中退火。低温加载流体Ar作为压力传递介质，保证了清洁的静液环境。Upsilon是通过原位时间分辨可见光（Si）或红外（Ge）干涉测定法测定的。Upsilon随压力呈指数增长，其特征为负活化体积为- 0.46-OMEGA（其中OMEGA为原子体积），Si为- 0.28-OMEGA。Si中的活化体积与掺杂剂浓度和掺杂剂类型无关。非晶相的结构弛豫对upsilon没有显著影响。这些和其他结果与所有的体点缺陷机制不一致，但与迄今提出的所有界面点缺陷机制一致。提出了spepen - turnbull界面悬垂键机制的动力学分析，假设沿界面边缘处悬垂键的热生成，悬垂键沿边缘的独立迁移以重建从无定形到晶体结构的网络，以及悬垂键“陷阱”处的单分子湮灭动力学。模型收益率upsilon = 2 sin(θ)upsilon-sn (r) exp((δs (f) +δs (m)) / k) exp -[(δh (f) +δh (m)) / kT],在δs (f)和δh (f)的标准生成焓熵和一双悬空键,δs (m)和δh (m)的熵和焓的运动的悬空键界面,upsilon-s声速,θ是{111}的错位,n (r)是啤酒花的净数量由悬空键之前湮灭。它半定量地解释了测量的前因子、取向依赖性、活化能和upsilon的活化体积，以及“自由能突变”的压力，超过这个压力，由于悬空键迁移障碍的消失，SPEG的指数压力增强不能不间断地继续下去。掺杂对upsilon的增强可以解释为界面上带电悬空键数量的增加，而中性数没有变化。定量模型的掺杂依赖的upsilon严格审查。在低浓度下，数据可以用分数电离或广义费米能级移动模型来解释；列举了进一步测试这些模型的方法。离子辐照可能通过改变界面悬空键的居群来影响upsilon，或者可能涉及任何类型的体点缺陷撞击界面并转化为悬空键，但是当离子束关闭时，upsilon不会受到这些突然减少的缺陷的到达率的限制。它也可能涉及与界面上悬空键的热生成并行操作的替代点缺陷机制。
The effects of hydrostatic pressure on the solid-phase epitaxial growth (SPEG) rate upsilon of intrinsic Ge(100) and undoped and doped Si(100) into their respective self-implanted amorphous phases are reported. Samples were annealed in a high-temperature, high-pressure diamond anvil cell. Cryogenically loaded fluid Ar, used as the pressure transmission medium, ensured a clean and hydrostatic environment. Upsilon was determined by in situ time-resolved visible (for Si) or infrared (for Ge) interferometry. Upsilon increased exponentially with pressure, characterized by a negative activation volume of - 0.46-OMEGA in Ge, where OMEGA is the atomic volume, and - 0.28-OMEGA in Si. The activation volume in Si is independent of both dopant concentration and dopant type. Structural relaxation of the amorphous phases has no significant effect on upsilon. These and other results are inconsistent with all bulk point-defect mechanisms, but consistent with all interface point-defect mechanisms, proposed to date. A kinetic analysis of the Spaepen-Turnbull interfacial dangling bond mechanism is presented, assuming thermal generation of dangling bonds at ledges along the interface, independent migration of the dangling bonds along the ledges to reconstruct the network from the amorphous to the crystalline structure, and unimolecular annihilation kinetics at dangling bond "traps". The model yields upsilon = 2 sin (theta)upsilon-sn(r) exp[(DELTA-S(f) + DELTA-S(m))/k] exp -[(DELTA-H(f) + DELTA-H(m))/kT], where DELTA-S(f) and DELTA-H(f) are the standard entropy and enthalpy of formation of a pair of dangling bonds, DELTA-S(m) and DELTA-H(m) are the entropy and enthalpy of motion of a dangling bond at the interface, upsilon-s is the speed of sound, theta is the misorientation from {111}, and n(r) is the net number of hops made by a dangling bond before it is annihilated. It accounts semiquantitatively for the measured prefactor, orientation dependence, activation energy, and activation volume of upsilon, and the pressure of a "free-energy catastrophe" beyond which the exponential pressure enhancement of SPEG cannot continue uninterrupted due to a vanishing barrier to dangling bond migration. The enhancement of upsilon by doping can be accounted for by an increased number of charged dangling bonds, with no change in the number of neutrals, at the interface. Quantitative models for the doping dependence of upsilon are critically reviewed. At low concentrations the data can be accounted for by either the fractional ionization or the generalized Fermi-level-shifting models; methods to further test these models are enumerated. Ion irradiation may affect upsilon by altering the populations of interfacial dangling bonds or may involve bulk point defects of any type impinging on the interface and converting to dangling bonds, but when the ion beam is turned off, upsilon cannot be limited by the arrival rate of these suddenly less-numerous defects. It may also involve alternative point-defect mechanisms operating in parallel with thermal generation of dangling bonds at the interface.