Electron transport properties of a narrow-bandgap semiconductor Bi2O2Te nanosheet

Abstract

A thin, narrow-bandgap semiconductor Bi2O2Te nanosheet is obtained via mechanical exfoliation, and a Hall-bar device is fabricated from it on a heavily doped Si/SiO2 substrate and studied at low temperatures. Gate transfer characteristic measurements show that the transport carriers in the nanosheet are of n-type. The carrier density, mobility, and mean free path in the nanosheet are determined by measurements of the Hall resistance and the longitudinal resistance of the Hall-bar device, and it is found that the electron transport in the nanosheet is in a quasi-two-dimensional (2D), strongly disordered regime. Magnetotransport measurements for the device at magnetic fields applied perpendicular to the nanosheet plane show dominantly weak antilocalization (WAL) characteristics at low fields and a linear magnetoresistance (LMR) behavior at high fields. We attribute the WAL characteristics to strong spin–orbit interaction (SOI) and the LMR to the classical origin of strong disorder in the nanosheet. Low-field magnetoconductivity measurements are also performed and are analyzed based on the multi-channel Hikami–Larkin–Nagaoka theory with the LMR correction being taken into account. The phase coherence length, spin relaxation length, effective 2D conduction channel number, and coefficient in the linear term due to the LMR in the nanosheet are extracted. It is found that the spin relaxation length in the Bi2O2Te nanosheet is several times smaller than that in its counterpart Bi2O2Se nanosheet, and thus, an ultra-strong SOI is present in the Bi2O2Te nanosheet. Our results reported in this study would greatly encourage further studies and applications of this emerging narrow-bandgap semiconductor 2D material.

High Mobility and Quantum Oscillations in Semiconducting Bi2O2Te Nanosheets Grown by Chemical Vapor Deposition

“…The aforementioned Bi 2 O 2 Se series’ works have led to increasing research interest in the investigation of the whole 2D Bi 2 O 2 X family, which possesses intriguing non-neutral crystal structures composed of alternatively stacked [Bi 2 O 2 ] n 2 n + layers and [X] n 2 n – layers, small electron effective mass, and tunable band gaps. − Compared to Bi 2 O 2 Se, Bi 2 O 2 Te was predicted to have smaller effective mass, larger spin–orbit coupling, and ferroelectricity under in-plane stress, suggesting the possible rich physics and more excellent electrical properties. , However, few studies of Bi 2 O 2 Te have been done so far, − probably attributed to its lack of efficient ways to achieve the growth of ultrathin Bi 2 O 2 Te films. Recent theoretical work on thermodynamics of growth in Bi 2 O 2 X family clearly pointed out that it is most difficult to synthesize stable Bi 2 O 2 Te because of the existence of various binary phases and the narrow window of chemical potential .…”