Non-equilibrium phase formation by 3MV electron irradiation

在超高压电子显微镜中用2 MeV电子辐照III-V族半导体化合物如GaAs、GaSb和InAs的单晶。电子辐照首先引起化学无序，随着电子辐照的继续，拓扑无序开始发生。随着辐照温度的升高，化学无序变得更难发生，并且因此拓扑无序被完全抑制。在低温下形成的拓扑和化学无序相在300 K时变得不稳定，并因此分别变成化学无序和有序相。在锌尖晶石结构中，随着化学无序度的增加，电荷分布不平衡，晶格畸变。认为结晶状态转变为拓扑无序状态（即，无定形状态）以缓和化学键的不稳定性。

Single crystals of Ill-V semiconductor compounds such as GaAs, GaSb and InAswere irradiated with 2 MeV electrons in a ultra-high voltage electron microscope. Electron irradiation first induces chemical disordering and with continued irradiation topological disordering sets in. The chemical disordering becomes more difficult to occur with increasing irradiation temperature and as a result of this the topological disordering is completely suppressed. The topologically- and chemically-disordered phases formed at low temperatures become unstable at 300 K, and as a result change into the chemically-disordered and ordered phases, respectively. In the zincblende structure, the charge distribution is unbalanced and the lattice is distorted with increasing the degree of chemical disorder. It is considered that the crystalline state transforms to the topologically-disordered states (i.e., an amorphous state) to relax the instability of chemical bonds.