Nanostructured MoS2 and WS2 Photoresponses under Gas Stimuli

Abstract

This study was on the optoelectronic properties of multilayered two-dimensional MoS2 and WS2 materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO2, and O2 environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS2 (n-type)/Si (p-type) and WS2 (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 × 105 cm−2 for WS2 thin film. The IV electrical results revealed that WS2 is more reactive than MoS2 film under different gas stimuli. WS2 film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 × 102 cm2/V. WS2 film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO2 environment was observed. Additionally, the external quantum efficiency of WS2 revealed a remarkable enhancement in the CO2 environment of 1.62 × 108 compared to MoS2 film with 6.74 × 106. According to our findings, the presence of CO2 on the surface of WS2 improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS2 as a photodetector under gas stimuli for future optoelectronic applications.

Self‐Powered UV Photodetector Utilizing Plasmonic Hot Carriers in 2D α‐MoO3/Ir/Si Schottky Heterojunction Devices

“…The PD parameters such as responsivity, EQE, detetctivity, and photocurrent gain are important parameters to understand the Ir layer effect. The results of these factors are calculated under 0 V bias based on the previous studies [ 24,34 ] and reported in Figure a. It is important to mention here that all results are calculated at 0 V bias voltage.…”

“…Based on the previous study of depositing different samples at different temperatures, it was found that 200 °C was better for optoelectronic and electronic applications. [24] The process of creating an ultrathin layer of Ir, which is only a few nanometers thick, was completed using a Leica EM ACE600 US sputter coater. The layer was deposited onto a high vacuum film surface that had a condition of 1E3 mbar.…”

“…Based on the previous study of depositing different samples at different temperatures, it was found that 200 °C was better for optoelectronic and electronic applications. [ 24 ]…”

“…However, recently the researchers did not detect a good photocurrent at 0 V by using MoO 3 /n-type Si. [23,24] The MoO 3 /Ir/Si PDs work by utilizing the MoO 3 layer as a hole transport layer, the Ir layer as a Schottky barrier, and the Si substrate as a charge collection layer. Light incident on the Ir metallic layer excites hot electrons, which are then transported through the Schottky barrier, leading to the formation of a photocurrent [30] this current can then be measured and used to determine the presence or absence of light.…”

Thermionic Emission of Atomic Layer Deposited MoO3/Si UV Photodetectors

“…Because a 5 V bias gave the sample more activations for better photoconductivity and a better photodetector response, we calculated the photocurrent gain, photoresponsivity ( ), external quantum efficiency (EQE), detectivity ( ), and finally the response/recovery time at 5 V biase. The calculations were collected based on the previous reports [ 54 , 55 , 56 ]. For a UV photodetector, the responsivity is important as it is a measure of the sensitivity of a photodetector to light.…”