Electronic structure and spectral characteristics of Zn-substituted clathrate silicides

The results of complex theoretical studies of the electron structure of Zn-substituted Si-based clathrates are reported. The calculation is carried out by the linearized augmented plane wave method. As a result, the energy band structures, the total and partial densities of electron states, and the X-ray emission spectra are obtained. The effect of the number of substitutions and their sites in the unit cell on the electron-energy spectrum of clathrates is analyzed.     

Electron structure and spectral characteristics of Cd-substituted Ge-based clathrates

Theoretical data on the electron energy spectrum of the substituted clathrates in the Ba-Cd-Ge system with different content of Cd atoms are reported. The calculation is carried out by the method of linearized augmented plane wave. The energy band structures, the total and partial densities of electron states, and the X-ray emission spectra are obtained from the calculations.     

Electronic and optical properties of ordered porous germanium

The electronic band structure and dielectric function of ordered porous Ge are studied by means of a sp³s^* tight-binding supercell model, in which periodical pores are produced by removing columns of atoms along [0 0 1] direction from a crystalline Ge structure and the pore surfaces are passivated by hydrogen atoms. The tight-binding results are compared with ab-initio calculations performed in small supercell systems. Due to the existence of periodicity in these systems, all the electron states are delocalized. However, the results of both electronic band structure and dielectric function show clear quantum confinement effects.     

电子结构的三防设计

电子结构在各种自然环境因素的综合影响下,面临着诸多失效形式,因此只有在设计阶段就注入环境防护理念,优选材料,优化结构再结合一定的工艺防护措施才能极大的提高电子产品对环境的适应性和产品使用的可靠性。     

Electronic structure of C60 films

A complete set of fundamental optical functions of fullerite (C₆₀) films in the range 1.5–7 eV is calculated from the known spectra of the imaginary and real parts of the dielectric permittivity. The total permittivity spectrum is expanded into elementary components. Three main parameters are determined for each component (the energy of the band maximum, the band half-width, and the oscillator strength). An interpretation of these components of the permittivity is proposed on the basis of published theoretical band calculations for fullerite. Fiz. Tekh. Poluprovodn. 33, 31–35 (January 1999)     

Characteristics, structure, and performance of a diffused-base germanium oscillator transistor

The diffused-base transistor structure affords a degree of design flexibility not found in previous structures. This is true because it has a larger number of independently adjustable design parameters than the previous structures. Its flexibility has been exploited in an oscillator transistor for 200-mc service. Design analysis shows that low ohmic base resistance, low collector body resistance, and operation at about 0.3 of the collector breakdown voltage are desirable in the present application. The methods of Lee have been used in making this germaniump-n-pdiffused-base unit. Alloyed emitter and base electrodes are parallel stripes approximately 0.5-mil apart, each measuring 1 × 6 mils. The collector is about 4.5 × 8 mils. Typical parameters at Vc= -10 volts and 1E= 10 ma are: fα= 600 mc,r'_{b}= 35 ohms, and Cc= 1.0 mmf. Median 200-mc oscillator efficiency of 50 per cent is obtained at the design bias point of -20 volts, 10 ma; this exceeds the performance objective. The unit withstands 20,000-gaccelerations in any direction, an additional demand imposed by the specific application for which it was developed.     

Electronic structure of insulator-confined ultra-thin Si channels

We consider ultra-thin Si channels terminated with (001) surfaces and confined by insulating media and discuss the dependence of the Si electronic structure on the channel thickness. We consider two types of the structural models: a vacuum-confined Si slab with the dangling bonds terminated by H atoms and a slab confined by α-quartz. The results of our ab initio calculations carried out using a periodic model and the PBE density functional demonstrate that both the band gap and the effective mass of Si slabs depends on the slab thickness and strongly suggest that this dependence should be taken into account in the device modeling.     

Nanoscale germanium MOS Dielectrics-part I: germanium oxynitrides

In this paper, nanoscale germanium (Ge) oxynitride dielectrics are investigated for Ge MOS device applications. The synthesizing methodology and physical properties of these oxynitride films have been examined first. Basic electrical characteristics have been acquired on metal-gated MOS capacitors with Ge oxynitride dielectric on substrates with different dopant types and crystal orientations. Using an optimized oxidation and nitridation recipe, high-quality Ge MOS capacitors with a minimal frequency dispersion and capacitance-voltage hysteresis have been demonstrated. In addition, the Ge oxynitride dielectric-substrate interface has also been analyzed with the combined low-frequency-high-frequency capacitance method that revealed a substantial reduction of interface trap density after the forming gas anneal. An asymmetric interface trap density distribution within the Ge bandgap has been mapped out, which might explain the inferior n-channel Ge MOSFETs with oxynitride dielectric. An abnormality in the general gate leakage behavior has been observed and found to originate from a transient charge-trapping effect.     

Electronic structure of memory traps in silicon nitride

From experiments on photoluminescence in Si₃N₄ the polaron energy of 1.4 eV was determined. This value is in agreement with the energy of thermal ionization determined from electron and hole transport. Quantum-chemical simulation showed that Si–Si bond is able to capture holes and electrons in Si₃N₄.     

Electronic structure of fullerene derivatives in organic photovoltaics

The electronic structures of the fullerene derivatives [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), [6,6]-diphenyl C₆₂ bis (butyric acid methyl ester) (bisPCBM), C₇₀, [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₀BM), [6,6]-phenyl-C₆₁-butyric acid butyl ester (PCBB), [6,6]-phenyl-C₆₁-butyric acid octyl ester (PCBO), [6,6]-thienyl-C₆₁-butyric acid methyl ester (TCBM), and indene-C₆₀ bisadduct (ICBA), which are frequently used as n-type materials in organic photovoltaics, were studied by ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy. We also performed molecular orbital calculation based on density functional theory to understand the experimental results. The electronic structures near the energy gap of the compounds were found to be governed predominately by the fullerene backbone. The side chains also affected the electronic structures of the compounds. The ionization energy and electron affinity were strongly affected by the number of carbons and functional groups in the side chain.     

Electronic structure and spectral properties of Si<Subscript>46</Subscript> and Na<Subscript>8</Subscript>Si<Subscript>46</Subscript> clathrates

The electronic structure of Si₄₆ and Na₈Si₄₆ clathrates has been calculated using the linearized augmented plane wave method. The calculation yielded their band structure, total and partial electron densities of states, and SiK_{β1, 3} and SiL_{2, 3} X-ray emission spectra. The calculated and experimental spectra for the Na₈Si₄₆ clathrate were compared.     

Copper-doped germanium detectors

Background limited operation of copper-doped germanium detectors has been obtained for a background as low as 10^-11watts (5 × 10³photons/second) in the 8-12 µ region. The temperature dependence of the observed responsivity for detectors, each containing the same copper concentration but having different donor concentration does not agree with any of the usual theories involving the free hole velocity, mobility, or capture cross section.     

Neutron-transmutation-doped germanium bolometers

Six slices of ultra-pure germanium were irradiated with thermal neutron fluences between 7.5×10¹⁶ and 1.88×10¹⁸ cm^?2. After thermal annealing the resistivity was measured down to low temperatures (<4.2K) and found to follow the relationship ρ = ρ₀exp(Δ/T) in the hopping conduction regime. Also, several junction FETs were tested for noise performance at room temperature and in an insulating housing in a 4.2K cryostat. These FETs will be used as first stage amplifiers for neutron-transmutation-doped germanium bolometers.     

Electronic structure of the Er-O6 complex in silicon

The energy diagram of the Er-O₆ complex in silicon is calculated. The square amplitudes of the wave functions of the complex on the erbium atom are determined. The results of our calculations show that the Er-O₆ complex is an acceptor in silicon. In addition, it is possible that the electron trap energy level is located in the energy gap of silicon. On the whole, the results of our calculations correspond to the Er-O quantum dot model proposed previously. Fiz. Tekh. Poluprovodn. 31, 1037–1044 (September 1997)     

Electronic structure mechanism for the wettability of Sn-based solder alloys

The developments of quantum theory, solid-state physics, and computational methods make it feasible to understand properties of materials by means of calculation. In this work, five octahedron clusters were designed to study the wettability of Sn-based solder alloys, which are applied in modern electronic mounting and packaging. Then, relativistic DV-Xα calculation, which is a molecular orbital method based on Hartree-Fock-Dirac approximation, was carried out. Heavy atoms, such as Pb, Bi, Sn, and Sb, were included in our clusters, so relativistic effects were taken into account in the calculation. The electronic parameter, Bo, the orbital interaction between atoms, was obtained through a Mulliken analysis of electronic structure. The electronic structure mechanism for the wettability of Sn-based solder alloys on a Cu substrate was put forward based on the analysis of orbital interactions between atoms. We believe that the wettability of the Sn_xM_y alloy would be improved only if orbital interactions between Sn atoms and Cu atoms are enforced because of the existence of the M element. The spreading and wetting behavior of Sn-based solder alloys were predicted and then explained by this quantum method on the basis of electronic structure theory. Predictions from analysis on calculation results were validated by wettability experiments and energy-dispersive x-ray (EDX) analysis.     

Improved germanium avalanche photodiodes

New kinds of germanium avalanche photodiodes with n+-n-p and p+-n structures were devised for improved excess noise and high quantum efficiency performance. Multiplication noise, quantum efficiency, and pulse response were studied and compared with those of the conventional n+-p structure diode. Multiplication noise of the new type of diodes were measured in the wavelength range between 0.63 and 1.52 μm. The effective ionization coefficient ratio of the p+-n diode was lower than unity at a wavelength longer than 1.1 μm and 0.6-0.7 at 1.52 μm, and that of the n+-n-p diode was 0.6-0.7 in the whole sensitive wavelength region. Response times were evaluated by using a mode-locked Nd:YAG laser beam and a frequency bandwidth wider than 1 GHz was estimated. Receiving optical power levels were compared with each other using parameters measured in this study.     

Electronic structure and carrier transport at laminated polymer homojunctions

Soft contact lamination, whereby films prepared separately from solution are brought into contact to form a single device, was used here to form homojunctions comprising two identical layers of poly(3-hexylthiophene) (P3HT) or two layers of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1′-3}-thiadiazole)] (F8BT). Using ultraviolet photoemission spectroscopy (UPS), Kelvin Probe Force Microscopy (KPFM), and current–voltage (I–V) measurements, the electronic structure of, and carrier transport across, these homojunctions were investigated. UPS and KPFM show that lamination does not introduce any significant offset in the molecular levels across the interface. The I–V characteristics confirm this result by showing that transport across the film is largely unaffected by the presence of the laminated interface. This important result means that lamination could become a versatile tool for constructing multi-layer polymer devices.     

Gate-self-aligned p-channel germanium MISFETs

The authors have fabricated the first gate-self-aligned germanium MISFETs and have obtained record transconductance for germanium FETs. The devices fabricated are p-channel, inversion-mode germanium MISFETs. A germanium-oxynitride gate dielectric is used and aluminum gates, serve as the mask for self-aligned source and drain implants. A maximum room-temperature transconductance of 104 mS/mm was measured for a 0.6-μm gate length. A hole inversion channel mobility of 640 cm² /V-s was calculated using transconductance and capacitance data from long-channel devices. This large hole channel mobility suggests that germanium may be an attractive candidate for CMOS technology