Morphological, optical and photovoltaic characteristics of MoSe2/SiOx/Si heterojunctions

J P B Silva,C Almeida Marques,J P Connolly,K Veltruská,K Gwozdz,L F Santos,A S Viana,E Popko,O Conde,V Matolín

doi:10.1038/s41598-020-58164-7

Abstract

This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe2 layers grown by chemical vapour deposition (CVD), using MoO3 and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe2 layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe2 layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe2/SiOx/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiOx/MoSe2 interface. A photovoltaic effect was observed with a short circuit current density (Jsc), open circuit voltage (VOC) and efficiency of −0.80 mA/cm2, 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe2 with improved photovoltaic response.

Highlights

It has recently been shown that two dimensional semiconductor transition metal dichalcogenides (2D TMDs) have solved the zero-band gap drawback of graphene
It is well known that mono-to-few layer MoSe2 can be grown by chemical vapour deposition (CVD), using MoO3 and Se as solid precursors, providing hydrogen is added to the carrier gas[2,9,10,23,24]
The relative amount of H2 in the total flowing gas that leads to similar layer morphology for different CVD reactors, depends on their specific characteristics, such as the temperature profile along the CVD furnace, which in turn imposes limits on the distance between the precursors’ holders

Summary

Introduction

It has recently been shown that two dimensional semiconductor transition metal dichalcogenides (2D TMDs) have solved the zero-band gap drawback of graphene. This H2% study shows that 8.3% of H2 in the total gas flux (sample B) allows the deposition of mono- to multilayer MoSe2 structures, with larger lateral sizes and covering a higher surface area.

Results

Conclusion