P. Vipin Kumar, Anagha P. Vincent, Srilakshmi Prabhu, S.G. Bubbly, S.B. Gudennavar
Department of Physics and Electronics, CHRIST University, Bangalore-560029, Karnataka, India
## Abstract
This study investigates the effectiveness of nine inorganic semiconductor crystals − LiGaSe2, LiInSe2, CsHgInS3, SnS, GaTe, BiI3, Sb2Te3, Tl4CdI6, and TlBr − for radiation detection applications based on photon and charged particle (electrons, protons, and heavy ions) interaction parameters. Mass attenuation coefficient (μ/ρ), half value layer (HVL), relaxation length (λ), effective atomic number (Zeff), electron density (Neff), equivalent atomic number (Zeq), and exposure buildup factor (EBF) were computed using PAGEX software. These results, along with their intrinsic efficiencies calculated, were compared with that of standard materials (NaI(Tl), CdZnTe, and CdTe). The μ/ρ values of the studied semiconducting materials are ranked in the decreasing order as: TlBr, Tl4CdI6, BiI3, CsHgInS3, Sb2Te3, GaTe, SnS, LiInSe2, and LiGaSe2. TlBr, Tl4CdI6, BiI3, and Sb2Te3 show superior photon detection capabilities compared to the reference materials. TlBr and Tl4CdI6 have the highest intrinsic efficiency across nearly all energy regions, while LiGaSe2 has the lowest. Interaction parameters like range and Zeff for charged particles were also computed using standard databases, with SnS and Sb2Te3 showing the least range for all the charged particles studied throughout the entire energy region. The study indicates that TlBr and Tl4CdI6 have strong potential for developing next-generation radiation detectors with enhanced sensitivity, addressing needs in healthcare and national security.
## Introduction
Semiconductors, a pivotal class of materials with the ability to conduct and control electrical currents with precision, have revolutionized the electronics industry, powering devices from smartphones and laptops to medical equipment and renewable energy systems. With applications ranging from artificial intelligence and the internet of things to autonomous vehicles, semiconductors serve as the fundamental components enabling limitless technological possibilities (Yamazaki et al., 2019; Jeschke et al., 2020; Bhalerao et al., 2022). Semiconductors also serve as excellent radiation detectors, offering high energy resolution and efficiency, which makes them especially ideal for X-ray and γ-ray spectroscopy (Luke et al., 2005). Inorganic semiconductors, particularly compounds like thallium bromide (TlBr) and
Cadmium Zinc Telluride (CdZnTe), are widely used in medical imaging, astronomical X-ray imaging and modern radiation detection technologies (Sellin, 2003) owing to their higher density (∼7.56 g cm−3 for TlBr and ∼5.85 g cm−3 for CdZnTe) and effective atomic number (Zeff ∼ 60 at 1 MeV for TlBr and Zeff ∼ 45 at 1 MeV for CdZnTe) compared to silicon (Si) and germanium (Ge). While traditional semiconductors like high-purity Si and Ge offer high sensitivity and energy resolution, compound semiconductors outperform them in certain radiation detection applications, delivering superior efficiency, sensitivity, energy resolution, and faster response times (Owens and Peacock, 2004; Milbrath et al., 2008). This work evaluates the efficacy of nine inorganic semiconductor single crystals − lithium gallium selenide (LiGaSe2), lithium indium selenide (LiInSe2), gallium telluride (GaTe), thallium bromide (TlBr), thallium cadmium iodide (Tl4CdI6), bismuth iodide (BiI3), antimony telluride (Sb2Te3), tin sulphide (SnS), and cesium mercury indium trisulfide (CsHgInS3) − for radiation detection applications.
The optical properties of ternary chalcopyrites LiGaSe2 and LiInSe2 have been widely investigated (Tupitsyn et al., 2012; Stowe et al., 2013). They are chemically and physically stable and have band gaps of 3.57 eV and 2.85 eV, respectively. The resistivity of these materials is of the order of 108 − 1011 Ω cm. Given that 6Li has a high neutron capture cross section and Li being part of the LiBC2 structure, these semiconductors are of interest as prime candidates for room-temperature neutron detection. Meanwhile, GaTe, another chalcogenide semiconductor, with a distinctive layered structure and moderate band gap (1.67 eV) (Reshmi et al., 2011), can serve as a promising candidate in high energy radiation detectors. On the other hand, TlBr, with its atomic number combination of 81 and 35, high density (7.56 g cm−3), and short mean free path (mfp ∼1 cm at 511 keV, where, mfp is the distance over which the radiation intensity decreases to 1/e of its initial value), potentially offers excellent detection efficiency at higher photon energies (Sellin, 2003; Kim et al., 2020). Furthermore, its wide band gap (2.68 eV) and high resistivity (∼1010 Ω cm) make it particularly suitable for room-temperature radiation detection (Oliveira et al., 2004; Kim et al., 2020). Recently, it has gained significant attention due to its unique properties, making it suitable for applications in Compton imaging, gamma camera imaging, and neutron-based crystalline characterization (Watanabe et al., 2020; Lee and Park, 2022; Hitomi et al., 2024). Tl4CdI6, a tetragonal crystal exhibiting excellent photoconductivity, high density (6.87 g cm−3), a resistivity of 1010 Ω cm and band gap of 2.80 eV, has immense potential in room-temperature X-ray and γ-ray detection (Wang et al., 2014). Moving forward, BiI3 is another candidate with a wide energy band gap and high atomic absorption coefficient making it a promising room-temperature radiation detector, displaying a resistivity of around 1012 Ω cm (Garg et al., 2014). Meanwhile, Sb2Te3, featuring a rhombohedral structure and narrow band gap (0.21 eV), is a promising absorbing material in optoelectronic devices, with scope for futuristic applications in low-energy radiation detection. Furthermore, the p-type semiconductor SnS with a band gap of 1.53 eV is an attractive material for photo detector application. It has a high photon absorption efficiency in the soft X-ray region (Hegde et al., 2011). Additionally, CsHgInS3, having a high specific density and band gap of 2.3 eV, is a good candidate for X-ray and γ-ray detection. While other applications of these semiconductors have been widely studied, this paper offers a novel contribution by focusing on the investigation of their radiation detection properties, an area that is of prime interest to nuclear physics, radiation physics, medical physics and high-energy astrophysics communities.
Understanding the intricate radiation interaction parameters of semiconductors is paramount for accurately quantifying energy deposition and assessing the compound's effectiveness. At the core of detector materials lies the radiation-matter interaction, which involves energy transfer and absorption, forming the bedrock of detector functionality. Evaluating detector effectiveness necessitates subjecting it to a diverse array of energy and radiation types, followed by meticulous calculation of radiation interaction parameters. Thus, this study assumes a pivotal role in systematically assessing the reliability and effectiveness of selected inorganic semiconducting compounds, thoughtfully chosen from existing literature, for radiation detection applications. The investigation revolves around scrutinizing their detection effectiveness against various photons (X-/γ-ray) and charged particles.
Variety of computational software tools have been developed to compute the interaction parameters of photons and charged particles, including XMuDat (Nowotny, 1998), XCOM (Berger and Hubbell, 1999a, Berger and Hubbell, 1999b), GEANT4 (Agostinelli et al., 2003), WinXCom (Gerward et al., 2004), Phy-X/PSD (Şakar et al., 2020), Phy-X/ZeXTRa (Özpolat et al., 2020), and PAGEX (Prabhu et al., 2021a). These tools have been extensively used in the computation of radiation interaction parameters of various materials, such as glasses (Kavaz et al., 2019; Kavun et al., 2024; Yorulmaz et al., 2024), alloys (Yaykaşlı et al., 2022), and perovskites (Prabhu et al., 2023). In this study, computation of photon interaction parameters have been meticulously executed using PAGEX software, as detailed elsewhere (Prabhu et al., 2021a). Furthermore, the range of heavy ions and electrons has been carefully determined through the utilization of the SRIM Monte Carlo software (Ziegler et al., 2010) and ESTAR database (Berger et al., 2005), respectively. The significance of these parameters has been elucidated in detail in our previous works (Prabhu et al., 2021a; Prabhu et al., 2021b), highlighting their critical role in advancing radiation shielding and detection technology.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/radiation-attenuation-parameters-and-intrinsic-efficiency-of-a-few-semiconductor-crystals-for-radiation-detection-applications.html