In this talk, I will focus on my experimental studies in semiconductor and molecular spintronics. I will first briefly describe spin transport in a persistent photoconductor Si-doped Al_0.3Ga_0.7As, where we produced the first results of spin lifetimes at various carrier densities on one and the same device. I will then talk about molecular patterning and directed self-assembly of Au nanoparticles on GaAs [1].

Combining the expertise from these two projects, my main project is aimed at chirality-induced spin selectivity (CISS) in hybrid semiconductor/molecular devices [2]. We obtained definitive evidence of spin-selective electron transport in two-terminal vertical junctions of (Ga,Mn)As/AHPA-L molecules/Au. The use of the ferromagnetic semiconductor (Ga,Mn)As resulted in the realization of a pronounced and stable CISS-induced spin-valve effect, which facilitated, for the first time, a comprehensive and rigorous study of its bias dependences. The results are in apparent violation of the fundamental Onsager reciprocity, and constitutes a significant constraint on any viable theory of the CISS and its device manifestations. Finally, I will present probable observation of the Hanle effect and dynamic nuclear polarization in the junctions of n-GaAs/AHPA-L molecules/Au, which are free of any magnetic material. Our results have practical implication in electrically creating and possibly detecting spin polarized current in semiconductors without using any magnetic material.

References:

[1] T. Liu, et al., ACS Appl. Mater. Interfaces 9, 43363 (2017).

[2] T. Liu, et al., ACS Nano 14, 15983 (2020).