Date/Time: 04-03-2018 - Tuesday - 05:00 PM - 07:00 PM
Vishakha Kaushik1 Deepak Varandani1 Pintu Das1 Bodh Raj Mehta1

1, Indian Institute of Technology Delhi, New Delhi, , India

In the present study, two-dimensional (2D) material molybdenum disulfide (MoS2), deposited using chemical vapour deposition is studied for its interesting electrical, optical and mechanical properties, as a function of number of layers. Raman spectroscopy has been employed to obtain the magnitude of difference between E2g (~385cm-1) and A1g (~404cm-1) peaks of MoS2 which has been used as a signature of the number of layers. The 2D MoS2 is characterized based on the nanoscale variations in the junction properties using Kelvin probe force microscopy (KPFM), conductive atomic force microscopy (CAFM) techniques and macroscale variations in the I-V characteristics, as a function of number of layers. The surface potential values obtained using KPFM technique, gives the effective value of work function for different number of layers of MoS2. For efficient implementation of 2D materials in electronic and optoelecronic devices, it is imperative to form a good metal-semiconductor contact. The metal-semiconductor junction is studied as a function of applied loading force and number of layers of MoS2 using CAFM. The I-V characteristics are obtained with two different AFM metal tips in contact mode, namely, Cobalt (Co) and Platinum (Pt), which should form an Ohmic and Schottky contact with MoS2, theoretically. However, experimental investigation of I-V characteristics using CAFM shows the formation of Schottky barrier and hence a rectifying contact due to Fermi level pinning even for the Co metal electrode contact. The study emphasizes the critical influence of singlelayer nature on the metal contacts in novel 2D materials based devices. Metal – 2D semiconductor contact studied nanoscopically and junction behavior analyzed gives insights for the device formation for photodetector applications. In order to substantiate the layer dependence of MoS2 samples on the optoelectronic properties, photoresponse measurements (I-t characteristics) have been studied macroscopically using Keithley 2400 sourcemeter with a two-electrode configuration. The photoresponse behavior of thin film MoS2 is observed at different wavelengths of light. The photoresponsivity changes from 12.48 for monolayer sample to 4.79 for multilayer sample due to the optically generated carriers for the typical white light wavelength. Photoelectrical measurements on layer dependent, poly-crystalline MoS2 samples show excellent sensitivity, fast photoresponsivity and good reproducibility as a photodetector. The study shows the critical role played by the number of layers on the electronic and optical properties of MoS2 based devices.

Meeting Program

5:00 PM–7:00 PM Apr 3, 2018

PCC North, 300 Level, Exhibit Hall C-E