RESEARCH INTEREST
I. SEMICONDUCTOR NANOMATERIALS
I have been using self-designed physical and chemical vapor deposition techniques to synthesize 0D metal, 1D metal-oxide, and 2D metal chalcogenides/halide semiconductor nanomaterials. The synergy of the physical properties of low dimensional nanomaterials make the potential use in nanostructured devices. During synthesis, we can control the size, optical, electronic, and crystalline properties of nanomaterials.
II. PHOTOLUMINESCENCE
The properties of metal-semiconductor (MS) heterojunctions have been studied through the photonic view. Using laser of quantized energy, the electron transitions across the MS junction are studied. We have shown how the presence of MS junction can alter of the photoluminescence (PL) properties of the nanomaterials. Moreover, the formation of MS heterojunction can induce the PL properties in nanomaterials. So far we have studied PL properties of the NbO2, Zn, ZnO, Zn/ZnO, Bi/Bi2O3, CrI3, etc. nanomaterials. PL characterization involves investigations of the excitons and transport of carriers across the MS heterojunctions at low temperatures.
III. NANOELECTRONICS
We developed a probe station to measure the electronic transport properties of MS heterojunctions. It involves studies at low temperatures to investigate the tunneling current (carriers) through such MS heterojunctions, electron hopping properties, etc. The metal ball-probe technique helps to measure the average electronic properties of the array of nanostructures. So far, we have studied nanostructure MS heterojunctions of Ta/NiO, Ta/NbO2, and Ta/TiO2, 2D CrI3 FET’s, etc.
IV. PHOTONICS
We used a custom-designed technique to study the magneto-optic properties of 1D NiO nanorods. We generated the two-magnon (2M) spin waves with magnon frequency of 43 THz, using a polarized laser. This is a first observation on the angle-resolved 2M spin waves in 1D NiO nanorods having the average length of ~700 nm and widths of ~100 nm. It is the smallest spin wave waveguide. The technique we developed can generate and measure the spin waves in waveguides of below 1 micron. However, the conventional Brillion light scattering (BLS) can measure the spin waves in the materials having dimensions of few microns.
V. ELECTROCHROMISM
We studied electrochromic (EC) properties of transparent 1D NiO nanorods grown on ITO. It shows the outstanding electrochromic properties, including very fast coloration and bleaching times (1.55 and 1.22 s). It is one of the fastest EC switching devices. Not only the half-cell but also studied full-cell 1D-WO3/1D-NiO EC devices. The 1D-WO3/1D-NiO EC devices show ultrafast (few microsecond) EC switching response, excellent stability and ability to block ultraviolet, visible and near-infrared lights (200-1100 nm). Therefore, 1D-WO3/1D-NiO EC devices are proposed to use for heat-shielding and curtaining smart windows.
VI. SUPERCAPACITORS
We investigate the impact of the nanosize on the supercapacitance in 1D nanorods and a 2D thin film of NiO. Using impedance spectroscopy, we proved that the low dimensionality in nanorods induces resistive nanocontacts that lead to poor performance of the supercapacitive device compared to the 2D thin-film of NiO. In addition, we have studied the impact of crystal phases and alterations in 3d valances on one-dimensional MoO2, MoO3, and Magnéli phase Mo4O11 nanorods-based supercapacitors.
