Mitigating valley-driven localization in atomically thin dopant chains in Si

Article

关键词: ONE-DIMENSIONAL SYSTEMS;    OFF-DIAGONAL DISORDER;    ANDERSON LOCALIZATION;    SCALING APPROACH;    SILICON;    TRANSITION;    ELECTRONS;    ARRAYS;   

DOI  :  10.1103/PhysRevB.94.115425

来源: SCIE

【 摘 要 】

A theoretical study of the localization properties of nanowires of dopants in silicon (Si) fabricated by ionic implantation or scanning tunnel microscope lithography is presented for a model incorporating the currently unavoidable imprecision in individual donor positioning. Experiments have shown that Ohm's law holds in some cases, in apparent defiance to the Anderson localization theory in one dimension. We investigate how valley interference affects the traditional theory of electronic structure of disordered systems. Each isolated donor orbital is realistically described by multivalley effective-mass theory. We extend this model to describe chains of donors as a linear combination of dopant orbitals. Disorder in donor positioning is taken into account, leading to an intricate disorder distribution of hoppings between nearest-neighbor donor sites (donor-donor tunnel coupling)-an effect of valley interference. A decay length, related to the usual localization length, is obtained for phosphorous (P) donor chains from a transfer-matrix approach and is further compared with the chain length. We quantitatively determine the impact of uncertainties delta R in the implantation position relative to a target and also compare our results with those obtained without valley interference. We analyze systematically the aimed interdonor separation dependence (R-0) and show that fairly diluted donor chains (R-0 = 7.7 nm) may be as long as 100 nm before the effective onset of Anderson localization, as long as the positioning error is under a lattice parameter (delta R < 0.543 nm).

【 授权许可】

Free