# Structure and Electrical Properties of Carbon-Rich Polymer Derived Silicon Carbonitride (SiCN)
###### Abstract
One of the ways to determine carrier mobility (\(\mu_{\rm H}\)), carrier type (n-type or p-type), carrier density/concentration (\(N\)), conductivity (\(\sigma_{\rm dc}\)) and other useful electrical conductivity parameters in a semiconductor is through Hall measurement. The principle and efficiency of Hall measurement technique for the assessment of semiconductivity in shaped crystal articles and thin films have been emphasized [18; 19]. Usually, semiconductor materials either possess a majority positive or negative charge carriers signifying p-type or n-type semiconductors, respectively. However, some materials appear to have played out the two charge carrier types as majority carriers at the same time under different conditions. In a recent study aimed at characterizing the electrical properties of SiCN(O) PCDs, [PERSON] et al. revealed that some samples gave both positive and negative signs of Hall coefficient, but it could not be inferred as to whether the samples were of p-type or n-type semiconductors [16]. Similarly, the question of why a single material possesses both positive and negative Hall coefficient (i.e., both n and p-type majority charge carriers) is still a subject of unresolved debate [20; 21]. The compositions, processing conditions, and the nanostructure of the materials could be the intrinsic source of these observations. For instance, after assessing the effect of thermal treatments on the electrical conductivity of SiCN and SiCN ceramics, [PERSON] et al. recently reported that addition of boron increased the on-set crystallization temperature of SiCN PDC because boron retarded the atomic mobility, and the Si(B)CN ceramic showed higher RT conductivity than the as-pyrolyzed SiCN ceramics [22]. Besides the use of metal addition to improve electrical properties, conscious formation of sp\({}^{2}\) hybridized carbon phases by raising the carbon content can also help increase electrical properties of PDCs. This can be achieved via custom-made precursor synthesis [23], mixing of different commercially available precursors [24] or direct addition of a suitable crosslinker [25; 26]. Among these approaches, it is the direct addition of a suitable cross-linker that is the most straightforward and easy. Divinylbenzene (DVB) is a common cross-linking agent used to adjust the resulting chemical and structural composition of PDCs by increasing the carbon content and molecular weight/ceramic yield [27]. The resulting formation of sp\({}^{2}\) hybridized carbon phase from the rise in carbon content has been shown to be beneficial to electrical properties [28; 26]. The type of the inert atmosphere adopted during thermal treatment has also been identified as a crucial factor that determines electrical conductivity behaviour via carbothermic composition adjustments [9]. In [9], [PERSON] et al. investigated the influence of ammonia (NH\({}_{3}\)) alone and argon (Ar)/ammonia gas mixture atmosphere on thermally induced RT conductivity of SiCN and reported that free carbon content of the materials is reduced due to enhanced methane evolution in the ammonia (NH\({}_{3}\)) atmosphere, resulting in a progressive replacement of carbon by nitrogen and this led to decrease in RT electrical conductivity by up to 4 orders of magnitude. Consequently, the electrical conductivity of semiconductor engineering ceramics can also be modified through the choice of pyrolysis atmosphere. So far, some applications of electrically conducting carbon rich PDCs where tailoring the chemical composition could influence the properties of the ceramics and make them of functional use have been displayed in batteries or electrocatalysis [29, 30, 31]. Motivated by the exceptional properties of carbon rich PDCs that have evolved in the recent past and the high temperatures stability of SiCN PDCs, it is believed that a tailor-made chemical composition of carbon rich SiCN could hold prospects for novel discoveries in other application areas such as thermopower or high temperature electronics that requires basically p-type and n-type semiconductors.