Borosilicate Glass Substrates Research Articles

Comparative study of aluminium-doped zinc oxide and ruthenium–aluminium co-doped zinc oxide by magnetron co-sputtering

Highly oriented polycrystalline aluminium-doped (Al-doped) and ruthenium–aluminium (Ru–Al) co-doped zinc oxide are prepared on borosilicate glass and polycarbonate (PC) substrates by co-sputtering at room temperature. To investigate the effect of Ru doping, co-sputtering is achieved by varying the sputtering power of Ru target while keeping the sputtering target power of Al-doped zinc oxide unchanged. Atomic force microscopy (AFM) data shows that the root-mean-square roughness of all the films is less than ∼ 2.5 nm. With Ru doping, the resistivity of the film improves by one order of magnitude as compared to pure Al-doped zinc oxide sample. The resistivity and carrier concentration values obtained correlated to the degree of crystallinity in the samples. High optical transmittance in the visible range are achieved (> 90% for borosilicate glass and > 80% for PC).

Synthesis of c-axis preferred orientation ZnO:Al transparent conductive thin films using a novel solvent method

Transparent aluminum doped zinc oxide (ZnO:Al, AZO) conducting thin films with a high-preferential c-axis orientation were synthesized using a new sol–gel formula. The films were deposited using a spin-coating route onto borosilicate glass substrates. We used propylene glycol methyl ether (PGME) as the solvent in place of ethylene glycol monomethyl ether (EGME), which is commonly used because it is easier to deposit onto the substrates. PGME is also superior in terms of health and safety. PGME solvent does not need to settle for several days before use and can be spin-coated as soon as the raw material and solvent are mixed. The effects of this novel solvent on the structural, morphological, electrical and optical properties are discussed using XRD, SEM, a four-point probe and UV–VIS spectrophotometry. It was found that the films produced with PGME showed a high-preferential c-axis orientation and compact microstructure in comparison films produced using EGME. The electrical resistivity of AZO thin films produced with PGME solvent was lowered to 3.474 × 10 − 3 Ω cm after annealing in 95 N 2/5H 2 atmosphere. In addition, the optical transmittances of AZO thin films on glass plates were higher than 90% in the visible wavelength region.

Stress and doping uniformity of laser crystallized amorphous silicon in thin film silicon solar cells

Simultaneous and locally resolved determination of the mechanical stress variation and the free hole concentration using Raman spectroscopy is demonstrated in laser crystallized amorphous silicon layers. Such layers are often used for the fabrication of thin film solar cells, e.g., on borosilicate glass substrates. The combined effects of stress and doping on the Raman signal can be separated based on the use of three wavelengths in the visible. The results show that the free hole concentration in the samples investigated varies between 1×1018 and 1.3×1019 cm−3. Stress as well as the free hole concentration vary substantially within the sample. The stress level varies between 575 and 850 MPa (±12 MPa). Cross-sectional transmission electron microscopy images show the presence of extended lattice defects such as dislocations and grain boundaries in the crystallized Si layer which could account for the lateral stress variations detected by Raman spectroscopy. The impact of film inhomogeneity in terms of stress and doping on the performance of a solar cell will be discussed.

Determination of dielectric constant and loss of high- K thin films in the microwave frequencies

A method to determine the dielectric constant and loss of high- K thin film dielectrics in the microwave frequency region using the extended cavity perturbation technique is presented. The feasibility of the technique is demonstrated by the determination of the dielectric constant and loss for reactively sputtered TiO 2 thin films on borosilicate glass substrates. The dielectric constant and loss is measured at 8.98, 9.96 and 10.97 GHz using a TE 10 n rectangular cavity. Using this technique, the dielectric properties of TiO 2 films deposited under varying oxygen percentage in the sputtering atmosphere from 20% to 100% were measured. The dielectric constant and loss are found to be dependent on both the oxygen partial pressure as well as frequency of measurement. The film deposited at 50% of oxygen had a higher dielectric constant, ε r = 44.35 at 8.98 GHz, where as the film deposited at 100% oxygen showed the lowest value of dielectric constant, ε r = 21.36 at 10.97 GHz. The dielectric loss tangent varied from 0.004 to 0.019 depending on frequency and oxygen partial pressure. However this technique is applicable only for thin films coated on low K dielectric substrates.

Optoelectronic and Interfacial Properties of CNT and ITO on Borosilicate Glass and PET Substrates with Nano- and Hetero-structural Aspects

AbstractNano- and hetero-structures of carbon nanotube (CNT) and indium tin oxide (ITO) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as sensing and actuators under cyclic loading. Optimized preparation conditions were obtained for multi-functional purpose of the specimens by obtaining the best dispersion and turbidity in the solution. Optical transmittance and electrical properties were investigated for CNT and ITO dipping and spraying coating on boro-silicate glass and polyethylene terephthalate (PET) substrates by electrical resistance measurement under cyclic loading and wettability test. Uniform dipping coating was performed using Wilhelmy plate method due to it simple and convenience. Specimen was applied with spraying coating additionally. The change in the electrical and optical properties of coated layer is mainly dependent upon the number of dip-coating, the concentration of CNT and ITO solutions, and the surface treatment condition. Electric properties of coating layers were measured using four-point probe method, and surface resistance was calculated using a dual configuration method. Optical transmittance of CNT and ITO coated PET film was also evaluated using UV spectrum. Surface energy and their hydrophilic and hydrophobic properties of CNT and ITO coated substrates were investigated by wettability test via static and dynamic contact angle measurements. As the elapsing time of cyclic loading passed, the stability of surface resistance and thus comparative interfacial adhesion between coated layer and substrates was evaluated to compare the thermodynamic work of adhesion, Wa. As dip-coating number increased, surface resistance of CNT coating decreased, whereas the transmittance decreased step-by-step due to the thicker CNT and ITO networking layer. Nano- and hetero-structural effects of CNT and ITO solution on the optical and electrical effects have been studied continuously.

Ion Channel Reconstitution on a Pore-Suspending Membrane on Microstructured Glass Chip: Towards Artificial Gap Junction Formation Between Bilayers and Cells

Chip based automated patch clamping is an attractive biophysical tool for studying ion channel proteins. Solvent-free planar lipid bilayers can be formed in an automated fashion by positioning and subsequent bursting of giant unilamellar lipid vesicles containing membrane proteins on micron-sized apertures in a borosilicate glass substrate. The use of proteoliposomes for bilayer formation on such chips allows for the direct recording of single channel activity without need for commonly difficult reconstitution of membrane protein after bilayer formation. This approach is specifically attractive for investigations of membrane proteins not accessible to patch clamp analysis, like e.g. proteins from organelles or proteins from bacteria.Here, the biophysical and pharmacological characterization of different membrane proteins was performed. A wide variety of ion channels have been studied with this technique, for example potassium channels (KcsA, Kv1.2), sodium channels (NachBac) as well as other ligand-dependent (IP3 receptor) or mechanosensitive channels (MscL, TRP channels). Also, screening for influx of antibiotics through porins (OmpF, OmpC) was done to elucidate the uptake kinetics of antibiotics through porins.One main set of experimental data to be presented is on connexins proteins. Connexins are widely distributed in mammalian tissues and serve to join cells together into larger, functional units. We investigated the properties of hemichannels from Cx26 and Cx43 which were isolated biochemically and reconstituted into synthetic lipid membranes. In this study, preliminary data suggest the formation of gap junctions between cells and synthetic bilayer membranes. This opens possibilities to access the cytoplasm of living cells for biochemical or electrical studies, and especially to develop novel automated techniques for electrophysiological studies.

Gold Nanoparticle-Assisted Laser Surface Modification of Borosilicate Glass Substrates

This paper describes the photomodification of borosilicate glass substrates assembled with 40 nm diameter gold nanoparticles (Au NPs) with surface coverages ranging from 17 to 23% on excitation of the localized surface plasmon band of the NPs with a 532 nm nanosecond pulsed-laser beam. The laser irradiation allowed the splitting and fusion of NPs on the substrate surface and, at the same time, the formation of craters of less than 10 nm diameter at various places following one laser shot with a relatively high intensity of 460 or 370 mJ·cm−2·pulse−1 but well below the breakdown threshold of 25−40 J·cm−2·pulse−1. The formation of the craters was more and more distinctly observed by continuous irradiations. The number density, average diameter, and the surface coverage of the craters were not linearly dependent on the laser shot number but exhibited the saturation behavior due to the consumption of Au NPs. The threshold laser energy for the crater formation was dependent on the accumulated number of laser shots: a greater number of laser shots were necessary to form craters as the laser fluence decreases. Most interestingly, the laser-irradiated areas of the substrate exhibited a greater susceptibility to the wet chemical etching with aqueous hydrogen fluoride. The mechanism of the laser modification and a possible application to nanofabrication on glass surfaces by utilizing Au NPs were discussed on the basis of the scanning electron microscopy (SEM) observation as well as the extinction and light scattering spectroscopic measurements.

Measurements of dielectric properties of TiO2 thin films at microwave frequencies using an extended cavity perturbation technique

This research provides a simple method to measure the dielectric properties of thin films at microwave frequencies. The cavity perturbation theory is applied to the measurement method. The measured frequency is in X-band (8.2–12.4 GHz). The titanium dioxide thin films are deposited by the RF reactive magnetron sputtering method onto borosilicate glass substrates. The microwave complex permittivity of films is then measured by the extended cavity perturbation technique. It was found the dielectric constants of titanium dioxide thin films strongly depend on the partial pressure of oxygen. The dielectric constant maximized at a value of 95 with 30% O2. This is the first report that confirms the high dielectric constant of TiO2 thin films at microwave frequencies which shows its potential for high-K related microwave devices.

Improved selectivity, response time and recovery time by [0 1 0] highly preferred-orientation silicalite-1 layer coated on SnO 2 thin film sensor for selective ethylene gas detection

In this work, sensing response, response time and recovery time for selective ethylene gas detection were improved by coating a layer of [0 1 0] highly preferred-orientation silicalite-1 polycrystals on SnO 2 thin film sensors. The sensors were prepared by primarily depositing SnO 2 on borosilicate glass substrates using ultrasonic spray pyrolysis technique. Conventional and [0 1 0] preferred orientations of silicalite-1 layers were then directly coated on the SnO 2 thin film sensors by hydrothermal crystallization technique with different gel compositions. The silicalite-1/SnO 2 thin film sensors were calcined at 550 °C in dry air. The crystal structure and surface morphology of SnO 2 and silicalite-1 layers were characterized by XRD and SEM techniques. XANES and TPR were used to verify oxidation state and reduction temperature of the SnO 2 thin film sensors, respectively. The interaction of C 2H 4 and H 2O with silicalite-1 was determined by TPD. The sensing performances, such as selectivity, dynamic range, response time and recovery time were evaluated for the C 2H 4 and H 2O. The results showed that the incorporated silicalite-1 layers readily improve the C 2H 4 selectivity and dynamic range by preferential adsorption of C 2H 4 molecules on the silicalite-1 filtering layers. The response time and recovery time for the [0 1 0] highly preferred-orientation silicalite-1/SnO 2 thin film sensor ( t 90%, 14 and 144 s) were shorter than those of the conventional one ( t 90%, 25 and 208 s). It is suggested that the [0 1 0] preferred-orientation silicalite-1, with a pore direction perpendicular to SnO 2 thin film surface, can accelerate the molecular diffusion and reduce the diffusion pathway of ethylene to the sensing film.

ZnO-based metal-semiconductor field-effect transistors on glass substrates

We investigate the influence of quartz glass and borosilicate glass substrates on the electrical properties of ZnO-based metal-semiconductor field-effect transistors (MESFETs). The n-type ZnO thin-film channels were grown by pulsed-laser deposition and MESFETs were processed by reactive dc sputtering of AgxO-Schottky gate contacts. All devices are in the normally-off state. They exhibit very low off-currents in the range of 10−13A and on/off ratios of maximum 6 decades. The channel mobilities are highest for ZnO on quartz with 1.3cm2/Vs. The glass substrates introduce a compensating effect on the conduction of the ZnO channel resulting in higher on/off-voltages and lower on-current.

A study on the thermal conductivity measurements of Cu thin films utilizing temperature distribution

Thin film type materials are widely used in high-tech industries including electronics, photonics and even machine tools. Often, knowledge of the thermal properties of thin films is needed to assess reliability through thermal stress analysis when the thin film type materials are applied to functional electronic parts. Only a few methods have been developed for thermal conductivity measurement of a thin film on a substrate. In this study Cu thin films were processed on the borosilicate glass substrate of prismatic bar shape using sputtering. Two Cu coated surfaces of specimens were brought into contact to maintain the insulated boundary conditions. The temperature distributions were measured from the back surface of the substrate using radiation thermometry. The thermal conductivities of the Cu thin films were measured and found to be much lower than those of bulk materials. The measured thermal conductivities were found to be closely related to the microstructures of the Cu thin films.

MOCVD of Zirconium Oxide from the Zirconium Guanidinate Complex [ZrCp′{η2-(iPrN)2CNMe2}2Cl

Parallel to successful studies into use of [ZrCp′{η2-(iPrN)2CNMe2}2Cl] as a precursor to the deposition of zirconium carbonitride via CVD the same precursor was utilised for the MOCVD of thin films of ZrO2 using borosilicate glass substrates. The deposited films were of mixed phase; films deposited at temperatures below 550 deg. C were predominantly orthorhombic (or tetragonal), whilst films deposited at 600 deg. C were approximately 1:1 mixtures of monoclinic and orthorhombic (or tetragonal) ZrO2. Additionally the monoclinic phase displayed preferred orientation. Compositional analysis showed that whilst the films had significant amounts of, principally graphitic, carbon contamination, which increased with increasing deposition temperature, chlorine contamination was negligible.

Rapid Thermal (RT) MOCVD of Undoped and Al Doped ZnO Thin Films

Undoped and aluminum doped zinc oxide thin films were deposited on Si (100) and borosilicate glass substrates by using a novel RT-MOCVD technique, which is based on the use of the thermal radiation of tungsten lamps for substrate heating. The films were deposited from the acetylacetonates of zinc and aluminum which were used as precursors in the presence of oxygen. As result, well ordered and homogeneous ZnO films were grown. The undoped films show a preferred orientation on both substrates while the grains of the polycrystalline aluminum doped films are randomly ordered. Additionally whisker growth was observed for the doped films. As confirmed by EDX analysis, the amount of aluminum dopant was precisely controlled by varying the flows of transport gas through the evaporators. Finally, it was found that all deposited films are optically transparent, with transmittance ratios between 65% and 85% in the visible range.

Raman scattering analysis of SiH bond stretching modes in hydrogenated microcrystalline silicon for use in thin-film photovoltaics

The presence of a pair of peaks in the high wavenumber infrared (IR) absorption region of hydrogenated microcrystalline silicon (μc-Si:H) has been recently proposed as a strong indicator of poor quality material that is prone to oxidation and is therefore unsuitable for thin-film, photovoltaic applications. In this work, we show that these peaks located at 2083 and 2100 cm −1 are also present in the Raman scattering spectra of μc-Si:H and therefore can be directly measured on substrates that are suitable for solar cells. We present results for material grown by matrix-distributed electron-cyclotron resonance (MD-ECR) plasma-enhanced chemical vapour deposition (PECVD) on both crystalline silicon and borosilicate glass substrates. The narrow, twinned peaks detected by Raman disappear with time—presumably due to oxidation—although a broad peak at 2100 cm −1 remains.

Microstructure–Property relationships in thin film ITO

Polycrystalline tin-doped indium oxide (ITO) thin films were prepared by pulsed laser deposition (PLD) with an ITO (In 2O 3–10 wt.% SnO 2) target and deposited on borosilicate glass substrates. By changing independently the deposition temperature and the oxygen pressure, a variety of microstructures were deposited. These different microstructures were mainly investigated not only by transmission electron microscopy (TEM) with cross-section and plan-view electron micrographs, but also by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction. Composition changes in ITO thin films grown under different deposition conditions were characterized by energy dispersive X-ray spectroscopy (EDX). The optical and electrical properties were studied respectively by UV–visible spectrophotometry and a four-point probe. The best compromise in terms of high transmittance ( T) in the visible range and low resistivity ( ρ) was obtained for films deposited between 0.66 and 2 Pa oxygen pressure ( P O 2 ) at 200 °C substrate temperature ( T s). The influence of P O 2 and T s on the microstructure and ITO film properties is discussed.

Effect of microstructural evolution on magnetic properties of Ni thin films

The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.

Processing optimization and optical properties of 3-D photonic crystals

Abstract The synthesis optimization of three-dimensional photonic crystals (direct and inverse opals) is discussed in terms of the influence of processing parameters on the final optical quality. A colloidal/sol–gel route, starting with the self-organization of polystyrene microspheres into opal structures by convective self-assembly, followed by infiltration with a dielectric matrix precursor sol and heat treatment, has been followed. Several substrate hydrophilization methods have been tested and different substrates. Sol–gel infiltration of the opal template interstices with silica was achieved by dip-coating or micro-syringe application and it was followed by removal of the polymeric template. The concentration of the colloidal sol, containing polystyrene spheres of 235 or 460 nm in diameter, was optimized. The structural and optical properties of the opals and inverse opals have been studied by field emission scanning electron microscopy and optical reflectivity spectroscopy, in order to assess the relationship between their structure and the photonic properties obtained. By using borosilicate glass substrates hydrophilized with hydrochloric acid, colloidal photonic crystals of good quality have been obtained, with well ordered regions up to ∼100 μm2. By monitoring the effective refractive index change with relative humidity of the surrounding atmosphere, using spectroscopic ellipsometry with an environmental chamber, it was concluded that the present photonic crystals are suitable for humidity sensing applications.

Influence of groove depth and surface profile on fluorescence enhancement by grating-coupled surface plasmon resonance

The fluorescence intensity of a sample placed on a metal grating pattern is enhanced due to excitation by the electric field of the grating-coupled surface plasmon resonance (GC-SPR). The dependence of the enhancement on groove depth and surface profile was studied with the aim of improving the sensitivity of fluorescence detection. The enhancement was found to depend on the groove depth, with intensity most enhanced on grating substrate of about 20 nm depth, which produced an intensity about 30 times greater than that on a flat borosilicate glass substrate. Rigorous coupled wave analysis calculation showed that the shape of the groove influenced GC-SPR, suggesting that controlling not only the depth but also the shape of the grating surface profile can be an important factor in improving the sensitivity of detection by fluorescence microscopy.

Growth and Applications of Nanocrystalline-Diamond Films

We have developed low temperature and large area nanocrystalline-diamond growth methods using microwave plasma-assisted chemical vapor deposition sustained by surface waves. Highly transparent and smooth nanocrystalline-diamond films were successfully grown on borosilicate glass, aluminum and other substrate materials by this method. Properties of our films were examined by using UV-excited Raman spectroscopy, X-ray diffraction, atomic force microscopy, and other techniques. Possible applications of our nanocrystalline-diamond films are discussed.

Synthesis and structural characterization of undoped and Co doped zinc oxide thin films obtained by aerosol assisted chemical vapour deposition

Dilute magnetic oxides are transparent, wide-bandgap materials that behave ferromagnetically when doped with a few percent of a magnetic 3d cation. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material, that is a prerequisite for successful fabrication of useful devices for the emerging technologies of spintronics. Here we report a study of growth characteristics and microstructural properties of undoped and Co doped ZnO films grown onto borosilicate glass substrates, using aerosol assisted chemical vapour deposition method. The obtained films are single phase, of Wurtzite type, some of them with a strong c-axis orientation, i.e. with the c-axis normal to the substrate surface.