Insights into the local electronic structure of semiconducting boron carbides in the vicinity of transition metal dopants

The Local Structure and I-V Characteristics of Chromium Doped Semiconducting Boron Carbide

“…The predicted local structure and spin configuration of Cr doped semiconducting boron carbide in chain system are shown in Figure 1. From spinpolarized calculation, Cr favors the state that the spins are roughly aligned in the same direction and the net spin magnetic moment on the Cr atoms is nonzero or at maxima [13]. This is similar to the expectations for Ti, V and Fe doping of semiconducting boron carbides [11,13].…”

“…The calculated local structure and spin configurations indicate that the transition metal (from Ti to Cu) energetically prefer to situate at the alternate sides of the chain or symmetric axis when in molecular clusters [11,13]. Good agreement of the local structure has been obtained between the extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge fine structure (XANES) data for the Mn [11], Fe [10,11] and Co [11,12,16] doped boron carbides and the theoretical models [11].…”

“…The room temperature I-V characteristics, which were taken at 8000 and 0 Gauss magnetic field applied in the direction parallel to the direction of current, were compared. The local electronic structure and likely spin configurations of chromium doped boron carbide were recently calculated [11,13] by density function theory. All the first-principles calculations are performed in the framework of density functional theory as implemented in the DMol3 code [15].…”

“…The Mn, Fe and Co transition metal atoms dope boron carbide pairwise on adjacent icosahedra, which is in a good agreement with theoretical modeling of the local structure: two adjoined carborane cages each with a Mn, Fe and Co metal atom (forming the pair wise doping). The local spin configurations of all the 3d transition metal doped boron carbides, Ti through to Cu, are compared using theoretical cluster or icosahedral chain calculations [11,13]. The results suggest that transition metal doping will not only permit fabrication of boron carbide homojunctions but also may result in materials suitable for spintronic applications, particular in the case of chromium doped boron carbide [13], as suggested by other chromium metal doped materials [14].…”

The chromium site in doped glassy lithium tetraborate

“…Chromium is in many respects very similar, able to adopt a number of nominal valencies from zero valent chromium to chromium þ6 (i.e. [14,15], with very different consequences [15]. It is also known that the electronic properties of lithium borates may be manipulated by the direct inclusion of dopants, as well as, by the presence of Li þ , O, and dopant vacancies to serve as trap sites [10,16].…”