Deep-ultraviolet-light-driven reversible doping of WS₂ field-effect transistors

Abstract

Improvement of the electrical and photoelectric characteristics is essential to achieve an advanced performance of field-effect transistors and optoelectronic devices. Here we have developed a doping technique to drastically improve electrical and photoelectric characteristics of single-layered, bi-layered and multi-layered WS2 field-effect transistors (FET). After illuminating with deep ultraviolet (DUV) light in a nitrogen environment, WS2 FET shows an enhanced charge carrier density, mobility and photocurrent response. The threshold voltage of WS2 FET shifted toward the negative gate voltage, and the positions of E and A1g peaks in Raman spectra shifted toward lower wavenumbers, indicating the n-type doping effect of the WS2 FET. The doping effect is reversible. The pristine characteristics of WS2 FET can be restored by DUV light illumination in an oxygen environment. The DUV-driven doping technique in a gas environment provides a very stable, effective, easily applicable way to enhance the performance of WS2 FET.

Highly Stable and Tunable Chemical Doping of Multilayer WS2 Field Effect Transistor: Reduction in Contact Resistance

“…Figure 5a shows the first order Raman spectra of films agree well with the previous reports. 30,34,37 The chemically doped samples were also characterized by Raman spectroscopy. Figure 5a shows the Raman spectra of Pristine and doped 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The long-term stability of the doping of 2D materials is still a big challenge nowadays.…”

“…The improvement in drain current with doping is mainly due to these effects: (1) reduction in SB height with strong doping and (2) higher channel conductance arising from the increased electron concentration. 30 To quantify the effect of WS 2 doping on Au-WS 2 interface, we have extracted the contact resistance using two terminal transfer length method for doped and undoped device. …”

A comprehensive study on the effects of gamma radiation on the physical properties of a two-dimensional WS2monolayer semiconductor

“…They have shown n-type doping effect after DUV irradiation, and WS 2 -based FETs showed an enhanced charge carrier density, mobility and photocurrent response. 8 In an experimental investigation, the structural damage or degradation of 2D WS 2 crystal was observed by Atkin et al, when it was exposed to a laser beam in the presence of ambient moisture. 15 Ma et al demonstrated that Ar + ion irradiation creates S-vacancies in the WS 2 monolayer, resulting in an enhancement of the saturable absorption in the NIR region.…”

“…It spans a great diversity of atomic structures and physical properties. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Amongst them prominent 2D materials are transition metal dichalcogenides (2D-TMDCs). 1,2 A notable feature of the TMDCs is a transition from an indirect band gap to a direct band gap when thinned from bulk to a monolayer, which enhances significantly photoluminescence (PL) intensity.…”

“…20 Recently, extensive investigations have been made and many interesting novel phenomena have been discovered. 21 For instance, Iqbal et al 8 studied the effect of deep-ultraviolet (DUV) light in nitrogen (N 2 ) and oxygen (O 2 ) gas atmospheres on device performance of exfoliated single-, bi-, and multi-layered WS 2 FETs. They have shown n-type doping effect after DUV irradiation, and WS 2 -based FETs showed an enhanced charge carrier density, mobility and photocurrent response.…”