Thermal Stability Of Ge Research Articles

Optical and thermal stability of Ge-as-Se chalcogenide glasses for femtosecond laser writing

Chemically stoichiometric chalcogenide glasses of xGeSe2-(100-x)As2Se3 (x = 0, 20, 40, 60, 80) have been synthesized by using the melt-quenching method, and their optical and thermal stability for femtosecond laser writing have been investigated. It was found that, glass transition temperature increases while thermal expansion coefficient decreases with increasing Ge contents. The laser-induced damage threshold under 800 nm and 4.0 μm fs laser irradiation was also investigated. They are 183.8 and 323.97 mJ/cm2 at 800 nm and 4.0 μm for 80GeSe2-20As2Se3, being 1.61 and 2.02 times higher than the sizes of As2Se3 glasses, respectively. The introduction of Ge can significantly improve the optical and thermal stability of Ge–As–Se glasses that are promising in the application of high-stability photonic device prepared by femtosecond laser writing.

Thermal Stability of SiO2Doped Ge2Sb2Te5for Application in Phase Change Random Access Memory

Thermal stability of Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> (GST) and SiO<SUB>2</SUB> doped GST (SGST) films for phase change random access memory applications was investigated by observing the change of surface roughness, layer density and composition of both films after isothermal annealing. After both GST and SGST films were annealed at 325°C for 20 min, root mean square (RMS) surface roughness of GST was increased from 1.9 to 35.9 nm but that of SGST was almost unchanged. Layer density of GST also steeply decreased from 72.48 to 68.98 g/cm<SUP>2</SUP> and composition was largely varied from Ge : Sb : Te = 22.3 : 22.1 : 55.6 to 24.2 : 22.7 : 53.1, while those of SGST were almost unchanged. It was confirmed that the addition of a small amount of SiO<SUB>2</SUB> into GST film restricted the deterioration of physical and chemical properties of GST film, resulting in the better thermal stability after isothermal annealing.

Long-Wave Infrared-Transmitting Optical Fibers

Tellurium-enriched high-purity chalcogenide fibers were fabricated and their infrared (IR)-transmitting properties were investigated. The thermal stability of Ge–As–Te glasses could be improved significantly by introducing a small amount of selenium into the glasses, therefore allowing the production of structurally and optically homogeneous glass fibers with minimal scattering losses. The fibers with greater electrical conductivity (σ) showed higher transmission losses than those with smaller σ because of the severer free-carrier absorption in the former, which was identified by the temperature dependence of the fibers' attenuation. In an effort to reduce σ of the glass while maintaining its outstanding transmitting property in the long-wave IR region, iodine was added to replace a quantity of tellurium in the glass. The fiber made of Ge25Te58I7Se10 glass exhibited good transmitting property in the 4–12 μm region and showed losses as low as ∼1 dB/m around 9.5 μm.

Epitaxial growth and thermal stability of Ge 1− xSn x alloys on Ge-buffered Si(0 0 1) substrates

Single-crystal Ge 1− x Sn x alloys ( x=0.025, 0.052, and 0.078) with diamond cubic structure have been grown on Si(0 0 1) substrates by molecular beam epitaxy (MBE), using high-quality Ge thin films as buffer layers. The Ge 1− x Sn x alloys are nearly fully strained and have high crystalline quality without Sn surface segregation, revealed by the measurements of high resolution X-ray diffraction (HRXRD), Rutherford backscattering spectra (RBS), and transmission electron microscopy (TEM). In addition, thermal stability investigations show that the alloy with Sn composition of about 2.5% can be stable at 500 °C, which may enable it for device applications.

Thermal stability of Ge–As–Te–In glasses

The present paper reports the effect of replacement of Te by In on the crystallization kinetics and the thermal stability for Ge15 As20Te65−xInx (x = 0, 3, and 6 at.%) glasses. Differential scanning calorimetry (DSC) results under non-isothermal conditions for Ge15 As20Te65−xInx glasses were reported and discussed. The thermal stability of the studied glasses has been evaluated using various thermal stability criteria (� T, Hr, Hg and S), based on the characteristic temperatures such as the glass transition temperature (Tg), the temperature at which crystallization begins (Tc), the temperature corresponding to the maximum crystallization rate (Tp), or the melting temperature (Tm). Moreover, in the present work, the Kr(T) criterion has been considered for the evaluation of glass stability from DSC data. A comparison of various simple quantitative methods to assess the level of stability for Ge15 As20Te65−xInx (x = 0, 3, and 6 at.%) glasses is presented.

Thermal stability of nanoscale Ge metal-oxide-semiconductor capacitors with ZrO2 high-k gate dielectrics on Ge epitaxial layers

The authors report on the thermal stability of Ge metal-oxide-semiconductor (MOS) devices. Ge MOS capacitors with ZrO2 high-k gate dielectric and TaN metal gates were fabricated on Ge epitaxial films. Ge MOS capacitors exhibited a very low gate leakage current density of ∼1×10−6A∕cm2 with a capacitance equivalent thickness of 13Å. The excellent electrical characteristics, however, degraded when Ge∕ZrO2 gate stacks were subsequently annealed at elevated temperatures that are potentially used for transistor fabrication. The thermal degradation was due primarily to the formation of interfacial Ge oxides. Ge oxidation temperature was identified using surface analysis and correlated with electrical characteristics.

Thermal stability of photoinduced gratings and paramagnetic centers in Ge- and Ge/P-doped silica optical fibers

The electron-spin-resonance spectra of paramagnetic defects in Ge/P-doped silica fibers prepared with second-harmonic generation (SHG) are compared with those induced in Ge- and Ge/P-doped silica preforms by 5-eV photons. Among the defects observed, the thermal stability of Ge E'-type centers is similar to that of photoinduced Bragg grating efficiency but not of SHG efficiency. The isochronal anneal curves of the Ge(l) and Ge(2) centers in, Ge/P-doped silica correlate well with SHG efficiency, but the agreement is not nearly so good in silica containing only Ge. Only the thermal behavior of photoinduced Ge E'(d1) centers is similar to that of SHG efficiency in both materials, albeit only in the initial stages of annealing.

The Optical Properties and Stability of GE and Sn-Doped TEOx Films

ABSTRACTThe optical properties and the thermal stability of Ge and Sn doped TeOx films prepared by coevaporating TeO2, Te, Ge and Sn are reported. These films are amorphous as-deposited and crystalline Te appears after annealing at, e.g., 100 to 250°C. As expected, the addition of Ge and Sn increases the absorption of the TeOx films at the wavelength of interest (e.g., 830 nm). However, the thermal stability of (TeO1.1)1-xGex (x=0 to ~0.7) films is found to decrease with increasing x initially, starting to increase with increasing x only after x reaches a value between 0.3 and 0.4. These results differ from those reported previously for Ge and Sn-doped TeOx films and from those observed for Te-Ge alloy films. Interpretations of these results based on a solid state reaction between TeO2 and Ge or Sn during deposition are presented and discussed.