2D material GeS2 monolayer Ni doping Seebeck coefficient ZT values bipolar effect canning package cold pressing computer simulations conductivity contact resistances copper-based diamond-like compounds device diffusion barrier doped CdX compounds electric conductivity electrical contacts electronic transport figure of merit first-principles calculations half-Heusler high-throughput computing iron silicide isovalent doping jalpaite lattice conductivity material databases n-type Bi2Te3 powder processing power factor