In situ monitoring of resistivity and carrier concentration during molecular beam epitaxy of topological insulator Bi2Se3

Bismuth selenide (Bi2Se3) is a three-dimensional strong topological insulator of particular interest due to its relatively large bulk band gap (300 meV), single set of topologically non-trivial surface states, and layered van der Waals structure. However, there are outstanding problems in isolating the surface states of interest from bulk (trivial) conduction: this problem is frequently attributed to doping from selenium vacancies, and atmospheric exposure. To address these questions, we have constructed a system capable of growing thin film bismuth selenide by van der Waals epitaxy with the additional capability to do real time, in situ transport measurements, specifically resistivity and Hall carrier density. Post growth cooling to 15 K, and controlled exposure to atmospheric dopants is possible without breaking vacuum. We have demonstrated in-situ electrical measurements of resistivity and Hall effect which allow monitoring of the charge carrier density and mobility during growth as well as post-growth without breaking vacuum.