Executive Summary : | Much favoured hard radiation (X-ray and γ-ray) detection in semiconductors over scintillators is possible due to their photoconducting properties and the state-of-the-art materials are Si and Ge-based ones. Now a days, radiation detection by using semiconductors has found applications in defense, national security, research, medicine, and industry. Though Ge-based detectors are being used these days, they have serious limitations, especially since they require cryogenic conditions to prevent thermal noise. This prevents the widespread application of Ge-based detectors and room temperature (RT) nuclear detection materials are needed. Cd0.9Zn0.1Te (CZT), is considered to be the benchmark material for RT semiconductor detection. The factors favouring its superior ability being (1) wide band-gap (1.45-1.65 eV) (2) heaviness of its constituent elements and therefore, high density (5.8 g·cm-3). But quality crystal growth of CZT is a huge challenge. Practically, the requirements for an effective, RT detector material would be (1) resistivity ≥ 108 Ω·cm (2) band gap ≥ 1.5 eV (larger band gap prevents thermal excitation of carriers and therefore minimal dark current) (3) Heavy constituent atoms that can offer sufficient ‘stopping power’ for hard radiation (X-ray, γ-ray) detection (or in other words, density of the material should be greater than ~ 5 g·cm-3) (4) easiness of crystal growth. For a solid state chemist, this poses a great challenge due to the complimenting nature of the above said properties. e. g., heavy atoms will have larger valence orbitals that offer greater orbital overlap and smaller band gaps. Therefore, the ingredients and their properties should be 'just right' to favour the above conditions. The major ingredients to achieve the right combination of elements would be atomic radius, electronegativity difference, valence orbital type, stereochemical activity etc. Here, we propose an exploratory methodology inspired from the existing knowledge of semiconductor based detector materials, to design and discover brand new materials. Since the structure-bonding-property correlation and careful tuning of the physical properties will be required, we plan to study in detail, the crystallographic studies (by using X-ray diffraction), bonding and electronic structure (by using DFT based ab initio methods) as well as evaluation of physical properties of the semiconductors such as optical band gap and electrical conductivity. Our proposal is expected to pave way to new directions in detector technologies. Apart from the rich outcome of scientific knowledge, obvious beneficiaries of this successful project would be BARC, DRDO and other strategic sectors. |