3d transition metal doping of semiconducting boron carbides

Ni doping of semiconducting boron carbide

“…3͑b͒ was obtained after Ar ion sputtering, showing peaks that are characteristic of metallic Ni with low satellite structure and binding energies of 2p 3/2 = 852.1 eV and 2p 1/2 = 869.5 eV comparable to literature spectra for the metal, 18 consistent with the interstitial sites shown previously for transition metal dopants. 16,19 Similar measurements taken before surface sputtering ͓Fig. 3͑a͔͒ showed the existence of NiO with 2p 3/2 = 854.5 eV and 2p 1/2 = 872.2 eV and strong, characteristic satellite structure, indicating the presence of surface oxides.…”

“…The detection limit for this XANES setup is 10 ppm, and an order of magnitude estimate of the amount of Ni in the sample indicates a level of ϳ0.1%, significantly reduced from the proportion of Ni atoms in the precursor gas mix, which is calculated at close to 0.8%. These minute quantities of dopant atoms have a significant effect on the electronic properties, a characteristic of doping, quite distinct from the Co and Fe doped BC films, 19 with far higher impurity concentrations of ϳ1% within the film.…”

The local structure of transition metal doped semiconducting boron carbides

“…This PECVD approach is well established and has been successful in the fabrication of homojunction diodes [20][21][22][23][24][25] using 3d transition metal dopants to create an n-type material to the 'self-doped' slightly p-type undoped semiconducting boron carbide, as noted above and shown in figure 1 for some of the dopants studied here. Except for those fabricated with cobalt as the dopant, these homojunctions tend to preserve rectifying diode characteristics to temperatures well above room temperature.…”

“…For the related boron carbides, nickel [20,21,24,25] and iron [23] are certainly n-type dopants while cobalt may or may not [22] be a p-type dopant of the boron carbides, depending upon device temperature. The common route for semiconducting doping is to include a metallocene, M(C 5 H 5 ) 2 , M = V, Cr, Mn, Fe, Co, Ni, simultaneously with the carborane source molecule, during PECVD [20][21][22][23][24][25].…”

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

“…Semiconducting boron carbides are based on the packing of icosahedra [32], and may contain a significant amount of hydrogen [33], so defects are expected in this material. Successful boron carbide homojunctions have, nonetheless, been fabricated by plasma enhanced chemical vapor deposition (PECVD) of carboranes, with Ni [34,35], Co [32,36], Fe [37] and Mn [32] doping. Indeed, nickel doping of boron carbide has opened a route to the fabrication of the boron carbide based Esaki tunnel diode [34,35].…”