Germanium Isopropoxide Research Articles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Light-Activated Chemoresistive and Plasmonic-Resonant Optical Sensors for NO2 and H2 Sensing Based on ZnO Doped Nanoparticles

Self-organized growth of germanium nanocolumns

The crystalline germanium nanostructures were obtained on a silicon surface by the chemical vapor deposition technique using a germanium (IV) iso-propoxide ([Ge(OiPr)4]) metalorganic precursor as a germanium source. As was observed, the one-dimensional (1D) germanium nanostructures on the silicon surface form without using a metal catalyst, meaning that the formation of 1D nanostructures is based not on a vapor–liquid–solid (VLS) growth mechanism, but on self-organization processes which take place on the silicon surfaces during the CVD process of germanium iso-propoxide pyrolysis. Our observation suggests that the non-catalytic growth of germanium nanocolumns is strongly dependent on the CVD process temperature. The germanium phase composition and morphology have been investigated by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), and high resolution scanning electron microscopy (HRSEM), respectively. Our results provide a new way to grow 1D germanium nanostructures without contamination by a catalyst, which the vapor–liquid–solid growth mechanism is known to cause, allowing for the application of such materials in micro- and optoelectronics.

Physiochemical characterizations of electrospun (ZnO–GeO2) nanofibers and their optical properties

In this study, nanofiber mats consisting of two potential metal oxides were produced by electrospinning technique. An aqueous solution of zinc acetate dihydrate and germanium isopropoxide was mixed with polyvinyl alcohol solution to prepare a sol–gel that was electrospun at 20 kV. The obtained nanofiber mats were dried under a vacuum at 80 °C for 24 h and then calcined in air at different temperatures and soaking times. Physiochemical characterizations have affirmed that nanofibers composed of zinc oxide-germanium dioxide (ZnO–GeO2) can be prepared by calcination at different temperatures. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the Brunauer–Emmett–Teller (BET) technique were employed to characterize the as-spun nanofibers and the calcined product. The specific surface area of the calcined product decreased with increases in temperature. X-ray powder diffractometery (XRD) analysis was used to study the chemical composition and the crystallographic structure. The optical properties of the as-prepared ZnO–GeO2 nanofibers were also studied.

Preparation and spectroscopic studies of sol-gel derived GeO2/organically modified silane hybrid materials for optical waveguides

GeO2/organically modified silane organic-inorganic hybrid materials derived by a sol-gel technique were studied for optical waveguide applications. Acid-catalyzed solutions, firstly, γ-glycidoxypropyltrimetho-xysilane mixed with germanium isopropoxide, and secondly, methyltrimethoxysilane mixed with germanium isopropoxide were used as precursors. Optical and structural properties of the waveguide thin films prepared from the two types of sols were characterized by using the prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared. The obtained results indicate that in both cases, crack-free and highly transparent waveguide thin films with a thickness of more than 2-μm could be obtained by a single spin-coating process and at a low-temperature heat treatment of 100°C. A strong UV absorption region at short wavelength ∼200 nm, accompanied with a shoulder peaked at ∼240 nm, was also identified. It has been experimentally demonstrated that a channel waveguide structure could easily be fabricated from the hybrid sol-gel thin films by using reactive ion etching.

Preparation and optical properties of sol–gel neodymium-doped germania/γ-glycidoxypropyltrimethoxysilane organic–inorganic hybrid thin films

Germania/γ-glycidoxypropyltrimethoxysilane organic–inorganic hybrid spin-coating thin films doped with neodymium ions are prepared by a sol–gel technique and a spin-coating process. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane mixed with germanium isopropoxide are used as matrix precursors. Thermal gravimetric analysis, UV–visible spectroscopy, and Fourier transform infrared spectroscopy are used to study the structural and optical properties of the hybrid thin films. The results indicate that films that are crack-free and have a high transparency in the visible and near-infrared range can be obtained; a strong UV absorption region at short wavelength ∼200 nm, accompanied with a shoulder peaked at ∼240 nm, due to the neutral oxygen monovacancy defects, is also identified. Upconversion emission properties of the transparent dried gel and the thin films heated at different heat treatment temperatures and doped with different neodymium ion concentrations are studied; a relatively strong room-temperature yellow to violet upconversion emission at 397 nm (4D3/2→4I13/2) is observed under a xenon lamp excitation with yellow light at the wavelength of 580 nm (4I9/2→4G5/2). The effect of Nd3+ doping concentration and heat treatment temperature on upconversion emission of the thin films is also studied. The mechanism of the upconversion is proposed.

Preparation and characterization of sol–gel processed GeO2/methyltrimethoxysilane hybrid thin films

Abstract We report on preparation and characterization of GeO2/methyltrimethoxysilane hybrid thin films processed by the sol–gel spin coating technique. Acid catalyzed solutions of methyltrimethoxysilane mixed with germanium isopropoxide have been used as precursors for the hybrid materials. The optical properties of the thin films, including refractive index, thickness, and transparency as well as structural characterization, have been studied by using a prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV–visible spectroscopy, and Fourier transform infrared spectroscopy. The results indicate that a crack-free, low absorption, and high transparency in the visible range optical films with a thickness of about 1.3 μm could be obtained by a single spin-coating process and at low heat treatment temperature. A strong UV absorption region at short wavelength ∼200 nm, accompanied with a shoulder peaked at ∼240 nm, due to the neutral oxygen monovacancies defects, has also been identified.

Germania/ormosil hybrid materials derived at low temperature for photonic applications

We report on germania/organically modified silane (ormosil) hybrid materials produced by the sol–gel technique for photonic applications. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane mixed with germanium isopropoxide have been used as precursors for the hybrid materials. Planar waveguide films with a thickness of about 2 μm have been prepared by a single spin-coating process and low-temperature heat treatment from these high germanium content hybrid materials. Atomic force microscopy, thermal gravimetric analysis, UV–visible spectroscopy, and Fourier-transform infrared spectroscopy have been used to investigate the optical and structural properties of the films. The results have indicated that a dense, low absorption, and high transparency (in the visible range) waveguide film could be achieved at a low temperature. A strong UV-absorption region at short wavelengths ∼200 nm, accompanied by a shoulder peaked at ∼240 nm, has been noticed due to the neutral oxygen monovacancy defects. The propagation mode and loss properties of the planar waveguide films have also been investigated by using a prism-coupling technique.

Preparation, Microstructure and Physical Characteristics of Ferroelectric Pb5Ge3O11 Thin Films for Memory Application

ABSTRACTWe report sol-gel process of Pb5Ge3O11 (PGO) as well as the microstructure and physical properties of ferroelectric PGO films for memory applications. The PGO sol was prepared from lead acetate hydrate, germanium isopropoxide, and di(ethylene glycol) ethyl ether. The reactions taking place during the sol-gel process were examined in detail. Diethanolamine (DEA) was added to help maintain the desired species ratio and prevent germanium oxide precipitation. The preferred orientation of the PGO thin films was well controlled by the heating and reflux procedures in the sol-gel preparation process. Additionally, to examine the impact of postdeposition processing, selected samples were oxygen annealed at temperatures ranging from 450–650°C. The samples were characterized with X-ray diffraction (XRD), non-contact (planview) atomic force microscopy (NC-AFM). The resulting data indicate that the microstructure and physical properties of PGO films depend strongly on the precursor preparation as well as the post deposition annealing temperature.

Deposition and properties of spin on Pb5Ge3O11 ferroelectric thin film

This paper will discuss the spin on deposition of Pb5Ge3O11(PGO) on Ir and ZrO2 substrates for MFMIS and MFIS FeRAM applications. The precursors used are lead acetate trihydrate and germanium isopropoxide in di (ethylene glycol) ethyl ether. After optimizing the deposition conditions of spin speed, baking condition and annealing condition, single phase c-axis PGO has been obtained on both Ir and ZrO2 substrates. The film deposited on Ir substrate shows extremely smooth surface and very well saturated square shape hysteresis loop. The 2Pr is about 6∼8 μC/cm2, dielectric constant is about 50∼100, and the leakage current is about 3×10−6 A/cm2 at 100 kV/cm for 100–120nm thickness PGO thin film. The PGO thin film deposited on ZrO2 is also very uniform. About 0.7V memory window observed for 180nm PGO thin film with 13nm ZrO2 high-k gate dielectric at 2V sweep voltage. The leakage current is about 2.5×10−7 A/cm2 at 100 kV/cm

Crystallization and transformation of amorphous GeO2 derived from hydrolysis of germanium isopropoxide

The cristobalite and α-quartz forms of GeO2 crystallize on prolonged heating at 675–770 °C of amorphous GeO2 prepared by hydrolysis of Ge(OC3H7)4. The cristobalite is transformed into α-quartz in the later stages of heating. On heating at a rate of 10 °C min–1, only the α-quartz crystallizes above 810 °C. The kinetics of crystallization of α-quartz from an amorphous phase has been studied by means of X-ray diffraction. The crystallization isotherms are described by the Avrami equation ln(1–f)=–ktn with n= 4, the activation energy being 276 kJ mol–1. A mixture of the cristobalite and α-quartz forms has been ground in air. The cristobalite is transformed into rutile. The transformation mechanism is discussed. On grinding, α-quartz is converted into the amorphous form. The rutile form, prepared by grinding, is transformed into α-quartz at 1 010–1 050 °C on heating at 10 °C min–1.