Studies on DC transport and terahertz conductivity of granular molybdenum thin films for microwave radiation detector applications

Abstract

The morphological, transport and terahertz optical properties of DC magnetron sputtered granular molybdenum thin-films with nano-grains embedded in an amorphous matrix have been studied in the normal and superconducting states. The superconducting transition temperatures of these films are much higher than that of bulk molybdenum. The optical properties of these thin-films have been studied using terahertz time-domain spectroscopy. Their properties have been compared with the existing materials used for the development of radiation detectors. The resistivity of the films lies in >100 µΩ-cm range which is ideal for making highly sensitive radiation detectors. The Hall measurements indicate the presence of holes as the dominant carriers with very small mean free path and mobility. In the normal state, the films are disordered bad metal but they have large superfluid density and stiffness in their superconducting state. The normal state and superconducting properties of the films are very promising for their use in cryogenic radiation detectors for microwave, terahertz, and far IR frequency ranges.

Temperature-Dependent Structural, Dielectric, and Raman Spectroscopy Studies on Magnetoelectric Co4Nb2O9

“…The details of the experimental setup can be found elsewhere. 32 ■ RESULTS AND DISCUSSION Temperature-Dependent Dielectric and Isothermal Magnetodielectric Measurements. The temperature-dependent ε′ and tan(δ) of CNO in the absence of magnetic field at different frequencies are presented in Figure 1a,b, respectively.…”

“…An averaging of 500 spectra is done to improve the signal to noise ratio. The details of the experimental setup can be found elsewhere …”

Terahertz dielectric properties of Fe3O4 thin films deposited on Si (100) substrate

“…At first the complex optical conductivity of reference substrate is measured For this, the Si substrate was placed in one of the slots of the sample holder (figure 2(a)) at the bottom of the VTI of the cryostat and the other slot was kept empty. At each temperature, the electric field amplitudes of THz beam passed through a 10 mm empty circular window (wos) and the reference substrate (ws) was measured [24,25]. In the second experiment, the electric field amplitudes of the THz beam passed through the reference substrate (ws) and the film on the substrate (wf ) was measured at the same temperatures where the optical properties of the substrate were measured earlier [24,25].…”

“…At each temperature, the electric field amplitudes of THz beam passed through a 10 mm empty circular window (wos) and the reference substrate (ws) was measured [24,25]. In the second experiment, the electric field amplitudes of the THz beam passed through the reference substrate (ws) and the film on the substrate (wf ) was measured at the same temperatures where the optical properties of the substrate were measured earlier [24,25]. The wos & ws and ws & wf were placed one after the other on the THz beam path using a stepper motor attached to the insert.…”

“…The N f from the THz spectra is estimated iteratively by minimizing the error between the experimental data and theoretical function at each frequency using the Nelder-Mead simplex algorithm [24]. From the N f = n f + i k f (n f -the refractive index of the film, k f -extinction coefficient of the film), σ 1 and ϵ 1 are estimated respectively as σ 1 = 2ϵ 0 ωn f k f , and…”