GaAs中的N-nH复合物在原子尺度上的截面扫描隧道显微镜研究
N-nH complexes in GaAs studied at the atomic scale by cross-sectional scanning tunneling microscopy
摘要：
氮（N）掺杂的GaAs的氢化允许通过操纵N-nH络合物（N-nH络合物，其中氮原子被n个氢（H）原子包围）来可逆地调节带隙和产生位点受控的量子点。在这里，我们采用横截面扫描隧道显微镜（X-STM）在原子尺度上研究这些复合物在GaAs（110）表面。此外，我们进行了密度泛函理论（DFT）计算，以确定N-nH复合物的原子性质。我们认为，在（110）GaAs表面或附近的两个H原子从N-nH复合物解离为H $_2$分子。我们观察到多个功能相关的氢化过程中，其中一个子集被归类为N-1H配合物。这些与N-1H相关的特征显示出局部态密度（LDOS）的明显降低，这是GaAs（110）表面中N原子的特征，并且具有位于三个晶向之一的LDOS的额外的明显局部增强。N-nH特征可以用STM尖端操作。显示在一种情况下，在两个镜像对称状态之间的切换行为，并在另一种情况下，去除局部增强的LDOS。明亮对比度的消失很可能是从N-nH络合物中去除H原子的标志。
英文摘要：
Hydrogenation of nitrogen (N) doped GaAs allows for reversible tuning of the bandgap and the creation of site controlled quantum dots through the manipulation of N-nH complexes, N-nH complexes, wherein a nitrogen atom is surrounded by n hydrogen (H) atoms. Here we employ cross-sectional scanning tunneling microscopy (X-STM) to study these complexes in the GaAs (110) surface at the atomic scale. In addition to that we performed density functional theory (DFT) calculations to determine the atomic properties of the N-nH complexes. We argue that at or near the (110) GaAs surface two H atoms from N-nH complexes dissociate as an H$_2$ molecule. We observe multiple features related to the hydrogenation process, of which a subset is classified as N-1H complexes. These N-1H related features show an apparent reduction of the local density of states (LDOS), characteristic to N atoms in the GaAs (110) surface with an additional apparent localized enhancement of the LDOS located in one of three crystal directions. N-nH features can be manipulated with the STM tip. Showing in one case a switching behavior between two mirror-symmetric states and in another case a removal of the localized enhancement of the LDOS. The disappearance of the bright contrast is most likely a signature of the removal of an H atom from the N-nH complex.
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