Electrical and optical properties of Co-doped and undoped MoS₂

Abstract

Co-doped and undoped layered MoS 2 crystals were grown by the chemical vapor transport method using iodine as the transport agent. Both reflectance and piezoreflectance measurements reveal two exciton transitions of the direct band edge around 1.86 and 2.06 eV for undoped MoS 2 and 1.84 and 2.03 eV for Co-doped MoS 2 . Hall effect measurements show that the Co-doped MoS 2 sample has a lower carrier concentration and mobility than the undoped sample. These differences between undoped and Co-doped MoS 2 were attributed to the effect of cobalt atoms causing a small lattice distortion, lattice imperfections and/or impurity states that form trap states between the conduction band and valence band. Furthermore, photoconductivity (PC) and persistent PC results show that Co-doped MoS 2 has a longer time constant and better responsivity than undoped MoS 2 . This work discusses the advantages of Co-doped MoS 2 for photodetector applications.

Photodriven Transient Picosecond Top‐Layer Semiconductor to Metal Phase‐Transition in p‐Doped Molybdenum Disulfide

“…[5] The semiconducting 2H-MoS 2 phase supports both n-and p-type doping induced by chemical and physical means. [7][8][9][10][11] Intercalation, electronic, optical, and thermal excitations as well as mechanical strain and layer orientation have been reported. [3,[12][13][14][15][16] Sliding the sulfur atoms of one of the S-planes in the S-Mo-S layers by 1.82 Å leads to A-B-C stacking within the monolayer, where the sulfur atoms occupy the centers of the hexagons of the 2H phase, which results in the metallic 1T-MoS 2 phase.…”

Enhanced Photoresponsivity of 2H-MoTe2 by Inserting 1T-MoTe2 Interlayer Contact for Photodetector Applications

“…It is observed that I ac /I dc of Ag contact on 2H-MoTe 2 decreases faster than that of 1T-MoTe 2 interlayer electrode contact as frequency increase. The behaviour of frequency dependence PC can be described by the relation [40]:…”

High Optical Response of Niobium-Doped WSe2-Layered Crystals

“…It can be observed that the I ac / I dc of Nb-doped crystal decreased faster than that of the undoped one as the frequency increased. The behavior of the frequency-dependent photocurrent can be described by the relation [43] Iac/Idc=k1×tanh(14fτ1)+k2×tanh(14fτ2) where K 1 and K 2 are the amplitude coefficients. τ 1 and τ 2 are the carrier time constants of long and short time decay processes.…”

“…Nevertheless, the slower time response in Nb-doped crystal might be due to the influence of trap states induced by niobium impurity doping. The trap states could deteriorate the carriers’ transfer speed in the doped crystal [43]. The slower response speed that arises from trap states could also correlate with the enhanced photoresponsivity in PC measurement.…”