Increasing Germanium Content Research Articles

The Properties of Amorphous Silicon Doped with the Isovalent Germanium Impurity

Dark conductivity, photoconductivity, index of refraction, absorption edge, and EPR of the layers of amorphous silicon (a-Si) doped with the isovalent germanium impurity are studied. The properties of a-Si are found to change nonmonotonically with increasing germanium concentration. At germanium concentrations of ≈ 3 at% a minimum of the refraction index and the dark conductivity as well as a maximum of the photosensitivity and the band gap (mobility gap) of a semiconductor are observed. Amorphous silicon with such a concentration of germanium is similar to a-Si:H in its properties. [Russian Text Ignored].

Magnetic Cluster Effects in FeSi1-xGex

Magnetization measurements on the solid solution FeSi1-xGex (x ≦ 0.5) have been performed between 2 and 900 K. For low germanium content (x ≦ 0.4) the susceptibility shows a temperature dependence similar to that of pure FeSi. The susceptibility behaviour of FeSi has previously been interpreted in a localized spin model where a nonmagnetic ground state is separated from a magnetic excited state by a small energy gap. Our experimental results on FeSi1-xGex indicate that the same model is applicable and that the energy gap decreases with an increase of germanium content and becomes zero at x ≅ 0.6.Magnetization measurements at low temperatures imply the presence of ferromagnetic clusters. The ordering temperature of the magnetic moments within these clusters is around 60 K for x = 0.5 and about 8 K for x = 0.4. For the germanium richest solid solution (x = 0.5) we estimate the average cluster size to be 30 μB at 4.2 K and assuming S = 1 about 20% of the iron atoms are located within these clusters.

Staebler-Wronski effects in hydrogenated amorphous Si 1−xGe x

Photo-induced defects in hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous Si 1−xGe x (a-Si 1−xGe x:H) created by prolonged light exposure and their effecton opto-electronic properties are studied. The nearly constant carrier lifetime in a-Si 1−xGe x:H with increasing germanium content shows that the states created by germanium dangling bonds in as-deposited a-Si 1−xGe x:H are situated near midband and that the spread of their distribution within the band gap may be small compared with that of the photo-induced metastable defect states. A relatively small Staebler-Wronski effect is observed in a-Si 1−xGe x:H. However, the density of photo-induced states in a-Si 1−xGe x:H is of about the same order of magnitude as that in a-Si:H. The reason for this seems to be that the large density of states created by germanium dangling bonds masks the effect of light-induced defects.

Silicon-Germanium-Boron Ternary Amorphous Alloy

Highly conductive ternary amorphous films are prepared by thermal decomposition of silane-germane-diborane mixtures in a low-pressure furnace at 500°C. The conductivity of the amorphous silicon-germanium-borom alloy exceeds the previously obtained limit for amorphous silicon, and increases with increasing germanium content. The d.c. conductivity and the Seebeck coefficient are measured at above room temperature. Measurements of the a.c. conductivity, optical absorption and E.S.R. are made at room temperature. The carrier transport is well described by a variable-range-hopping model. Evidences for a band model similar to that for the semimetal are proposed for the ternary amorphous alloy. In a higher germanium content film, the structure transforms into a microcrystalline one. The conductivity of microcrystalline silicon-germanium-boron alloy attains 103 S·cm-1.

Crystallization of amorphous GexSi100−x on SiO2

The growth kinetics of amorphous GexSi100−x (x ⩽ 0 ⩽ 100) films were studied using electrical measurements. The growth rate increases with increasing germanium content in the film and the activation energies change from 2.5 to 2.0 eV as the composition changes from x = 0 to x = 100.

Investigation of Luminescence in Ge‐Doped Sodalite Powders

A new class of cathodochromic materials, germanium‐doped sodalite:Br, are described. They exhibit both a bright luminescence at room temperature and a long lifetime, high contrast coloration mode. The effect of hydrogen annealing on the initial reflectance, luminescent intensity, and FB location are studied. The FB energy is shown to initially increase with increasing germanium concentration up to 9% and then to decrease with higher germanium concentration. A technique is outlined for determining the luminescence generated within a powdered sample that possesses an absorption band. This technique is used to determine the effect of electron beam coloration on the luminescent centers. It is shown that the formation of thermally erasable F centers quenches luminescent centers while the formation of optically erasable F centers does not.

The critical exponent for the spontaneous magnetization of iron-germanium alloys

The critical exponent β for the spontaneous magnetization near the Curie temperature has been measured for pure iron and binary iron alloys containing 5.7 5 at.% and 10.1 8 at.% germanium. It has been found that β slightly decreases with increasing germanium concentration.

Magnetic-field dependence of the rotational-hysteresis loss in nickel-germanium crystals

1. The rotational-hysteresis loss in Ni-Ge crystals in the (100) plane increases with increasing field, reaching a maximum at 800–1500 Oe; then it decreases, vanishing between 2000 and 3000 Oe. 2. The maximum loss is greater at lower germanium concentrations. 3. The maximum rotational-hysteresis loss shifts toward lower fields with increasing germanium concentration. 4. Even slight amounts of germanium significantly affect the anisotropy constant. 5. The changes in the anisotropy constant and in the saturation magnetization as functions of the germanium concentrations are proportional.

Effect of Germanium Additions on the Properties of “Malcolloy” in the System of Cobalt and Aluminium

Since the discovery of “Malcolloy” having high coercive forces in the system of cobalt and aluminium, investigations have been made on the effect of additions of nickel, molybdenum, titanium, vanadium, chromium, tungsten and manganese on the properties of Malcolloy, the highest coercive force obtained in each system of alloys being 1200∼1600 Oe. In this report, the effect of germanium additions on the properties of Co–Al alloys is examined, with the result that the coercive force of the alloys increases with increasing germanium content. An alloy composed of 81.80% Co, 9.20% Al and 9.00% Ge shows a coercive force of 1600 Oe, a residual magnetic flux density of 4200 G and a maximum energy product of 2.20 MG . Oe when tempered at 500°C for 125 hr after water-quenching from 1310°C. These alloys consist of many ferromagnetic elongated particles about 500∼1500 Å in length which are precipitated in the matrix of the nearly nonmagnetic β′ phase. The results show that the high coercivity of these alloys is mainly caused by the presence of single magnetic domain particles.