Abstract
The preferred orientation growth characteristics and surface roughness of polycrystalline bis-muth (Bi) thin films fabricated on glass substrates using the molecular beam epitaxy method were investigated at temperatures ranging from 18 to 150°C. The crystallization and morphology were analyzed in detail and the polycrystalline metal film structure-zone model (SZM) was modified to fit the polycrystalline Bi thin film. The boundary temperature between Zone T and Zone II in the SZM shifted to higher temperatures with the increase in film thickness or the decrease of growth rate. Furthermore, the effect of the thickness and surface roughness on the transport properties was investigated, especially for Bi thin films in Zone II. A two-transport channels model was adopted to reveal the influence of the film thickness on the competition between the metallic surface states and the semiconducting bulk states, which is consistent with the results of Bi single-crystal films. Therefore, the polycrystalline Bi thin films are expected to replace the single-crystal films in the application of spintronic devices.
Highlights
Semimetal Bi is one of the most well documented materials in solid-state physics because of its unique physical properties, such as low carrier density ($3 Â 1017 cmÀ3), small effective masses, long mean-free path (30 nm), highly anisotropic fermi surface and small band overlap at cryogenic temperature ($38 meV) (Marcano et al, 2010; Hofmann, 2006; Liao et al, 2014; Xiao et al, 2012)
In 1967, Sandomirskii first predicted that 30 nm was the critical thickness for the semimetal– semiconductor (SMSC) transition of Bi thin films caused by quantum-size effect (QSE) (Sandomirskii, 1967)
The thin films were grown at various substrate and explained the SMSC transition according to the compe- temperatures (18, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, titions of metallic surface states and semiconducting bulk 140 and 150C) using different deposition rates (1.61, 0.47, states (Xiao et al, 2012)
Summary
Semimetal Bi is one of the most well documented materials in solid-state physics because of its unique physical properties, such as low carrier density ($3 Â 1017 cmÀ3), small effective masses (me ’ 10À3), long mean-free path (30 nm), highly anisotropic fermi surface and small band overlap at cryogenic temperature ($38 meV) (Marcano et al, 2010; Hofmann, 2006; Liao et al, 2014; Xiao et al, 2012). Experimental contrast, the preferred orientation growth is mainly affected Bi thin films were fabricated on glass substrates using the by the surface energy rather than the lattice matching. The base pressure of the growth chamber was below substrates using the molecular beam epitaxy (MBE) method 2.0 Â 10À7 Pa. The thin films were grown at various substrate and explained the SMSC transition according to the compe- temperatures (18, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, titions of metallic surface states and semiconducting bulk 140 and 150C) using different deposition rates (1.61, 0.47, states (Xiao et al, 2012). Namba observed that the surface roughness on glass substrates prepared by a thermal evaporation method was directly affected by the high deposition rate and the substrate temperature XRD patterns of Bi thin films on glass at different substrate temperatures (the growth rate is 1.61 AminÀ1 and the deposition time is 240 min). (a) The XRD patterns of Bi thin films at substrate temperatures of 18, 30, 50, 60, 70 and 80C and (b) the XRD patterns of Bi thin films at substrate temperatures of 90, 100, 110, 120, 140 and 150C
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
