Photo-enhanced magnetization in semiconductors thin films incorporating magnetic dots

2000年，在580℃的高温下，在GaAs（001）衬底上交替沉积Fe和GaAs制备的半导体磁性复合薄膜在室温（RT）下的磁化增强已经被报道。虽然这对于未来的应用（如无线微电子机械系统）是一个非常令人鼓舞的成就，但光增强磁化（PEM）的起源仍然不清楚。部分原因是这些样品由多晶颗粒结构组成，其组成成分没有得到很好的设计和控制。本研究旨在确定PEM的关键材料并阐明其机理。在不同沉积顺序和衬底温度下，对Fe_3Ga_<2-x>、As_x和GaAs交替沉积制备的样品进行了系统研究，并对T_<s->的gan基复合结构进行了进一步的研究。结果表明，在T_s = 600℃下，以[100 nm GaAs/50 nm Fe_3Ga_<2-x>As_x/100 nm GaAs]为堆叠单元的分子束沉积制备的样品表现出明显的PEM效应。通过纳米电子探针分析的冶金学评价表明，超磁性金属Fe_3Ga_4是产生PEM的主要原因。讨论了该化合物是GaAs与Fe_3Ga_<2-x> as层间扩散的结果。粒子间相互作用模型的假设，是在2000年研究初期提出的。并不是所观察到的PEM效应的主要机制。对质子交换膜功率依赖性的系统研究表明，磁化强度的增加主要是由光致加热主导的，而纯光子激发也可能对质子交换膜有贡献，这表现在质子交换膜的大小超过了简单加热所能预期的最大值。这一新的效应应在今后的工作中进一步研究。少

Enhancement of magnetization by the light illumination at room temperature (RT) has been reported in the year 2000 for semiconductor-magnetic composite films prepared by the alternative deposition of Fe and GaAs on GaAs(001) substrates at high substrate temperature of 580 "C. While this was a very encouraging achievement for the future applications such as the wireless micro-electronic mechanical system, the origin of the photo-enhanced magnetization (PEM) has remained unclear. It was partly because of the fact that those samples consisted of polycrystalline, granular structures whose constituent ingredients were not well engineered nor controlled. This research was initiated with the aim to identify the key materials and elucidate the mechanism of PEM.Systematic studies of samples prepared by the alternative deposition of Fe_3Ga_<2-x>As_x and GaAs were carried out with various deposition sequences and different substrate temperatures T_<s-> GaN-based composite structures were also inv … More estigated. It was found that the samples prepared by molecular beam deposition with the stacking the unit of [100-nm GaAs/50-nm Fe_3Ga_<2-x>As_x/100-nm GaAs] at T_s = 600℃ exhibit significant PEM effect. Metallurgical evaluation by nano-electron probe analysis has revealed that metamagnetic metal Fe_3Ga_4 is responsible for the observed PEM. It was discussed that this compound was formed as a consequence of the interlayer diffusion process between GaAs and Fe_3Ga_<2-x>As. The hypothesis of the inter-particle interaction model, which was introduced at the initial stage of the study in 2000. was found not to be the principle mechanism for the observed PEM effect.Systematic studies on power dependence of PEM suggest that the increase of magnetization is primarily dominated by the light-induced heating, whereas pure photonic excitation may also contribute the PEM, as manifested itself by the fact that the magnitude of PEM exceeds beyond the maximum value that can be expected from simple heating. This novel effect should be pursued in the future work. Less