Thermal properties of two-dimensional crystal structures and their potential as a sensor

With the growing potential of two-dimensional (2D) materials in electronics and optoelectronics, the selection of suitable 2D materials for the development of high performance sensors has become more important. The use of more efficient and stable materials is important for device design. In this study, the stability calculations including structural, dynamical and thermal properties of transition metal dichalcogenides (TMD) and MXene materials as well as thermal expansion and work function calculations have been performed by using Density Functional Theory (DFT). The thermal stability of TMD structures were evaluated using different phases such as H, T, T', T'' and it was found that the calculated materials are stable up to high temperatures except for the T phase. Phonons, density of states, thermal expansion and heat capacities of pristine and surface-terminated Ti2C MXene structures were calculated by quasi-harmonic approximation. The highest thermal expansion coefficient obtained at room temperature belongs to the Ti2C structure terminated with oxygen atoms with a value of 2.43x10-5 K-1, while the Ti2C structure terminated with selenium atoms has the lowest thermal expansion coefficient with a value of 0.95x10-5 K-1. In the final section of this study, the adsorption energy and work function calculations of various metal atoms such as Cd, Hg and Pb and various gas molecules such as CO on TMD and MXene structures were performed to examine the potential of these 2D materials as sensors for the investigated atoms or molecules.