Tamura Kazuhisa, Mizuki Jun'ichiro
Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, Koto 1-1-1, Mikazuki-cho, Hyogo 679-5148, Japan.
J Phys Chem B. 2005 Jul 7;109(26):12832-6. doi: 10.1021/jp0455632.
The kinetics of the phase transition between the (2 x 2) and (p x square root[3])-Bi structures on Au(111) was investigated using electrochemical methods and time-resolved surface X-ray diffraction. The temporal changes in the current value and the diffracted X-ray intensity that originated from the (2 x 2)-Bi overlayer were monitored during the phase transitions at various over-potentials. The phase transition models and kinetics parameters were deduced from each of the current and X-ray intensity transient curves. We also carried out comparative studies of the phase transition from the structural and electrochemical points of view. For the (p x square root[3]) --> (2 x 2) phase transition, the phase transition models determined by the X-ray and electrochemical measurements were a surface-diffusion controlled instantaneous nucleation-growth process and a Langmuir process, respectively. For the reverse transition, the phase transition models determined by X-ray and electrochemical measurements were a Langmuir adsorption process and a surface diffusion controlled nucleation-growth process, respectively. Our results revealed that the current transient curve does not always reflect the phase transition model in both cases and suggest that a structural analysis is fundamental in the phase transition studies. The disagreements between the phase transition models and their mechanisms are discussed.
利用电化学方法和时间分辨表面X射线衍射研究了Au(111)上(2×2)和(p×√3)-Bi结构之间的相变动力学。在不同过电位下的相变过程中，监测了源于(2×2)-Bi覆盖层的电流值和衍射X射线强度的时间变化。从电流和X射线强度瞬态曲线中推导了相变模型和动力学参数。我们还从结构和电化学角度对相变进行了比较研究。对于(p×√3)→(2×2)相变，通过X射线和电化学测量确定的相变模型分别是表面扩散控制的瞬时成核-生长过程和朗缪尔过程。对于反向转变，通过X射线和电化学测量确定的相变模型分别是朗缪尔吸附过程和表面扩散控制的成核-生长过程。我们的结果表明，在这两种情况下，电流瞬态曲线并不总是反映相变模型，并表明结构分析在相变研究中是至关重要的。讨论了相变模型与其机制之间的分歧。
