Abstract
In this paper, MoS2 and Ni-MoS2 crystal layers were fabricated by the chemical vapor transport method with iodine as the transport agent. Two direct band edge transitions of excitons at 1.9 and 2.1 eV were observed successfully for both MoS2 and Ni-MoS2 samples using temperature-dependent optical reflectance (R) measurement. Hall effect measurements were carried out to analyze the transport behavior of carriers in MoS2 and Ni-MoS2, which indicate that the Ni-MoS2 sample is n-type and has a higher resistance and lower mobility than the MoS2 sample has. A photoconductivity spectrum was performed which shows an additional Ni doping level existing at 1.2 eV and a higher photocurrent generating only for Ni-MoS2. The differences between MoS2 and Ni-MoS2 could be attributed to the effect of Ni atoms causing small lattice imperfections to form trap states around 1.2 eV. The temperature-dependent conductivity shows the presence of two shallow levels with activation energies (84 and 6.7 meV in MoS2; 57 and 6.5 meV in Ni-MoS2). Therefore, the Ni doping level leads to high resistance, low mobility and small activation energies. A series of experimental results could provide useful guidance for the fabrication of optoelectronic devices using MoS2 structures.
Highlights
Transition metal dichalcogenides (TMDCs) have attracted great attention owing to their two-dimensional layer structure which is analogous to graphene [1,2]
Family, molybdenum disulfide (MoS2 ) with a direct bandgap is complementary to the graphene and suggests a great potential for logic devices, integrated circuits, and optoelectronics [3,4,5,6]
We have undertaken a series of experiments to analyze the optical and electrical properties of pure MoS2 and Ni-MoS2. Both MoS2 samples with and without the Ni dopant were prepared by the chemical vapor transport (CVT) method
Summary
Transition metal dichalcogenides (TMDCs) have attracted great attention owing to their two-dimensional layer structure which is analogous to graphene [1,2]. Most studies revealed that MoS2 ought to be n-type [19,20] Among these studies on dopants, little information has been published concerning the material and physical properties for Ni-MoS2 thin film. We have undertaken a series of experiments to analyze the optical and electrical properties of pure MoS2 and Ni-MoS2. In this paper, both MoS2 samples with and without the Ni dopant were prepared by the chemical vapor transport (CVT) method. A series of experiments results confirmed the Ni dopant effect on fundamental material properties which could provide guidance for further electronic and optoelectronic devices of MoS2
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