Philosophical Magazine B-physics of Condensed Matter Statistical Mechanics Electronic Optical and Magnetic Properties 

About: Philosophical Magazine B-physics of Condensed Matter Statistical Mechanics Electronic Optical and Magnetic Properties is an academic journal. The journal publishes majorly in the area(s): Amorphous silicon & Hubbard model. It has an ISSN identifier of 1364-2812. Over the lifetime, 51 publications have been published receiving 827 citations.

Hydrogen diffusion in amorphous silicon

Abstract: Hydrogen diffusion in doped and compensated a-Si:H has been measured by secondary-ion mass spectrometry profiling in the temperature range 155-300°C. Doping reduces the activation energy and enhances the diffusion coefficient by up to three orders of magnitude at 200°C, and a correlation between the diffusion coefficient and the dangling-bond density is found. An analysis of three different diffusion models indicates that the breaking of weak Si – Si bonds by hydrogen may be an important process. The relation between the diffusion results and the thermal equilibration of the electronic structure is discussed. The hydrogen diffusion coefficient in a-Si:H has been measured over the temperature range 155-300°C, with particular emphasis on the effects of doping and compensation. In all cases D H is thermally activated with an energy 1[sdot]2-1[sdot]5 eV. The diffusion coefficient decreases slowly with time which is attributed to the disorder-induced variation in site energies. We find that D H is gre...

Some electronic and metastability properties of a new nanostructured material: Hydrogenated polymorphous silicon

Abstract: When silicon thin films are deposited by plasma enhanced chemical vapour deposition in a plasma regime close to that of the formation of powder, a new type of material, called polymorphous silicon (pm-Si), is obtained. We present here the optoelectronic and stability properties of pm-Si films deposited from a mixture of silane diluted with hydrogen at total gas pressures in the range 800-1600 mTorr. A comparison with the properties of standard hydrogenated amorphous silicon (a-Si:H) is made. While some properties of both materials are similar, many others differ in a striking manner. Characterizations of as-deposited pm-Si films show that the best samples exhibit enhanced transport properties, such as the fact that the quantum efficiency-mobility-lifetime product eta mu tau is increased by a factor of 200-700 compared with that measured on a-Si:H under the same conditions. This correlates with a lower density of deep states. The kinetics of creation of defects, performed under 670 mW cm(-2) white light illumination and at a high temperature (100 degrees C) in order to attain a final steady state, have been studied, pm-Si samples exhibit faster kinetics of creation as well as of annealing of metastable defects than do a-Si:H samples. In their light-soaked state the best pm-Si samples exhibit eta mu tau products of the same order as those measured on device-grade a-Si:H in the annealed state. These enhanced transport properties, new properties and better stability are linked to the peculiar structure of pm-Si, namely ordered silicon nanoparticles embedded in an amorphous matrix.

Guinier-Preston zones observed by high-angle annular detector dark-field scanning transmission electron microscopy

Abstract: We have examined Guinier-Preston (GP) zones in aged Al-Cu alloys using atomic-resolution high-angle annular detector dark-field (HAADF) scanning transmission electron microscopy (STEM), together with conventional high-resolution transmission electron microscopy (HRTEM). Because the imaging of coherent Cu precipitates in an Al matrix by HAADF-STEM is less sensitive to the imaging conditions that would severely limit HRTEM, densely populated GP-1 zones are clearly observed. From the HAADF-STEM observations, we have found the GP-I zones to consist of two Cu layers, in addition to the commonly known monolayered GP-I zones. The structure of GP-II zones, in which Cu monolayers are separated by three Al layers, was identified, whereas a variant of GP-II zones does exist, for example double Cu layers separated by a single Al layer. In addition, in the GP-I stage, we have occasionally found Cu monolayers separated by three Al layers, which can be the incipient stage of GP-II zones. These results are in ge...

In-situ observation of the domain configurations during the phase transitions in barium titanate

Abstract: Using a polarizing optical microscope in conjunction with a charged-coupled device camera system, the domain microstructural evolution with respect to temperature in all three phases of BaTiO3 was studied. Along a (001) oriented section the domains in the tetragonal phase form 90° domain patterns in an ‘a—a’ configuration. The transition on heating and cooling between the cubic and tetragonal phases occurred near the same temperature, 125°C. On cooling, the domain structures in the orthorhombic phase appeared as a long continuous lamellar structure, while on heating the domains formed a ‘patchwork’ structure. This transition temperature showed a large thermal hysteresis. The final transition temperature from orthorhombic to rhombohedral was difficult to determine using this technique. The transition on cooling occurred at −134°C based on a colour change and the disappearance of all the domains. During heating, the domains reappeared at −110°C and remained in a patchwork structure throughout the o...

Optical absorption of non-interacting tight-binding electrons in a Peierls-distorted chain at half band-filling

Abstract: In this, the first of three articles on the optical absorption of electrons in half-filled Peierls-distorted chains, we present analytical results for non-interacting tight-binding electrons. We carefully derive explicit expressions for the current operator, the dipole transition matrix elements and the optical absorption for electrons with a cosine dispersion relation of bandwidth W and dimerization parameter δ. New correction (η) terms to the current operator are identified. A broad band-to-band transition is found in the frequency range Wδ < ω < W whose shape is determined by the joint density of states for the upper and lower Peierls subbands and the strong momentum dependence of the transition matrix elements.