Strong P-doping Research Articles

Strong interface p-doping and band bending in C 60 on MoO x

The electronic energy level evolution of fullerene (C 60) on molybdenum oxide (MoO x )/conducting indium tin oxide (ITO) interfaces has been investigated with ultra-violet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES) and atomic force microscopy (AFM). It was found that the thermally evaporated MoO x inter-layer substantially increased the surface workfunction. This increased surface workfunction strongly attract electrons towards the MoO x layer at the C 60/MoO x interface, resulting in strong inversion of C 60. Energy levels of C 60 relax gradually as the thickness of C 60 increases. An exceptionally long (>400 Å) band bending is observed during this relaxation in C 60. Such a long band bending has not been reported so far, for the organic/insulator (MoO x ) interface. The effect of air exposed MoO x inter-layer between ITO and C 60 has also been investigated. After air exposure of MoO x almost no band bending was observed and the electronic energy levels of C 60 remained more or less flat.

Thermal Conversion of Electronic and Electrical Properties of AuCl3-Doped Single-Walled Carbon Nanotubes

By using carbon-free inorganic atomic layer involving heat treatment from 150 to 300 °C, environmentally stable and permanent modulation of the electronic and electrical properties of single-walled carbon nanotubes (SWCNTs) from p-type to ambi-polar and possibly to n-type has been demonstrated. At low heat treatment temperature, a strong p-doping effect from Au(3+) ions to CNTs due to a large difference in reduction potential between them is dominant. However at higher temperature, the gold species are thermally reduced, and thermally induced CNT-Cl finally occurs by the decomposition reaction of AuCl(3). Thus, in the AuCl(3)-doped SWCNTs treated at higher temperature, the p-type doping effect is suppressed and an n-type property from CNT-Cl is thermally induced. Thermal conversion of the majority carrier type of AuCl(3)-doped SWNTs is systematically investigated by combining various optical and electrical tools.

A route to strong p-doping of epitaxial graphene on SiC

The effects of Au intercalation on the electronic properties of epitaxial graphene grown on SiC{0001} substrates are studied using first principles calculations. A graphene monolayer on SiC{0001} restores the shape of the pristine graphene dispersion, where doping levels between strongly n-doped and weakly p-doped can be achieved by altering the Au coverage. We predict that Au intercalation between the two C layers of bilayer graphene grown on SiC{0001} makes it possible to achieve a strongly p-doped graphene state, where the p-doping level can be controlled by means of the Au coverage.

Alkali vapour pressure variations during Na 2KSb(Cs) photocathode synthesis

A highly efficient semi-transparent multialkali antimonide Na 2KSb(Cs) photocathode was synthesized in situ by a standard procedure. The synthesis steps leading to p-doping of the Na 2KSb base layer, the creation of n-type K and Cs surface states, the creation of a Cs surface dipole layer and, finally to the formation of a Cs-Sb surface dipole layer or incorporation of Cs and Sb into an n-type surface compound are identified and explained. The addition and substitution reactions of alkali (sub) antimonide compounds, taking place during the synthesis of the homogeneous base layer, are considered thermodynamically using fairly reliable estimates of thermochemical functions. Alkali vapour pressure variations influencing the synthesis of the highly efficient photocathode are discussed. Excess Na in the residual atmosphere reacts with the evaporated Sb, giving an undoped heterogeneous base layer. Excess Cs reacts with the evaporating Sb, preventing strong p-doping of the base layer and leading to an unfavourable p-type Cs 3Sb saturated compound in the surface layer.

Electronic states in the gap of amorphous silicon-germanium alloys

The electron spin resonance spectra of a-Si 0.7Ge 0.3:H alloys are investigated as a function of doping with PH 3 and B 2H 6. Undoped and lightly-doped samples have Si and Ge dangling bonds as the main deep paramagnetic defects. From the doping dependence of the corresponding spin signals a higher average energy for the Ge dangling bond levels is deduced. The conduction band tail resonance (g = 2.0083) observed for strong P-doping is interpreted as due to fairly delocalized wavefunctions averaging over Si and Ge antibonding states. In contrast, the valence band tail states adjacent to the dangling bond levels are dominated by localized GeGe bonding orbitals.