The differences in energy between electronic bands due to valley splitting are of paramount importance in interpreting transport spectroscopy experiments on state-of-the-art quantum devices defined by scanning tunnelling microscope lithography. Using vasp, we develop a plane-wave density functional theory description of systems which is size limited due to computational tractability. Nonetheless, we provide valuable data for the benchmarking of empirical modelling techniques more capable of extending this discussion to confined disordered systems or actual devices. We then develop a less resource-intensive alternative via localised basis functions in siesta, retaining the physics of the plane-wave description, and extend this model beyond the capability of plane-wave methods to determine the ab initio valley splitting of well-isolated δ-layers. In obtaining an agreement between plane-wave and localised methods, we show that valley splitting has been overestimated in previous ab initio calculations by more than 50%.

Monolayer δ-doped structures in silicon have attracted renewed interest with their recent incorporation into atomic-scale device fabrication strategies as source and drain electrodes and in-plane gates. Modeling the physics of δ-doping at this scale proves challenging, however, due to the large computational overhead associated with ab initio and atomistic methods. Here, we develop an analytical theory based on an effective mass approximation. We specifically consider the Si:P materials system, and the limit of high donor density, which has been the subject of recent experiments. In this case, metallic behavior including screening tends to smooth out the local disorder potential associated with random dopant placement. While smooth potentials may be difficult to incorporate into microscopic, single-electron analyses, the problem is easily treated in the effective mass theory by means of a jellium approximation for the ionic charge. We then go beyond the analytic model, incorporating exchange and correlation effects within a simple numerical model. We argue that such an approach is appropriate for describing realistic, high-density, highly disordered devices, providing results comparable to density functional theory, but with greater intuitive appeal, and lower computational effort. We investigate valley coupling in these structures, finding that valley splitting in the low-lying Γ band grows much more quickly than the Γ-∆ band splitting at high densities. We also find that many-body exchange and correlation corrections affect the valley splitting more strongly than they affect the band splitting.

Objective Combined, nursing and allied health constitute most of the Australian health workforce; yet, little is known about graduate practice destinations. University Departments of Rural Health have collaborated on the Nursing and Allied Health Graduate Outcomes Tracking to investigate graduate entry into rural practice. Design Data linkage cohort study. Setting Monash University and the University of Newcastle. Participants Graduates who completed their degree in 2017 across seven disciplines. Main outcome measure(s) The outcome variable was Australian Health Practitioner Regulation Agency principal place of practice data. Explanatory variables included discipline, age, gender, location of origin, and number and duration of rural placements. Result Of 1130 graduates, 51% were nurses, 81% females, 62% under 21 years at enrolment, 23% of rural origin, 62% had at least one rural student placement, and 23% had over 40 cumulative rural placement days. At the time of their second Australian Health Practitioner Regulation Agency registration, 18% worked in a ‘Rural principal place of practice.’ Compared to urban, rural origin graduates had 4.45 times higher odds ratio of ‘Rural principal place of practice.’ For graduates who had <20 cumulative rural placement days, compared to zero the odds ratio of ‘Rural principal place of practice’ was the same (odds ratio = 1.10). For those who had 20‐40 rural placement days, the odds ratio was 1.93, and for >40 rural placement days, the odds ratio was 4.54). Conclusion Rural origin and more rural placement days positively influenced graduate rural practice destinations. Outcomes of cumulative placements days may compare to immersive placements.