Rms Roughness Values Research Articles

Highly Stable, Nanocrystalline, ZnO Thin-Film Transistor by Spray Pyrolysis Using High-K Dielectric

We report a highly stable, nanocrystalline, zinc oxide (ZnO) thin-film transistor (TFT) fabricated by spray pyrolysis using purified ${\text {ZrO}}_{x}$ as a gate insulator. The crystalline ZnO layer shows an average grain size of 30 nm and a smooth surface with an average rms roughness value of 1.21 nm. The smoothness of the ZnO film is due to the alignment of all grains with the (002) ${c}$ -axis. The TFTs exhibit a saturation mobility of 12.76 ${\text {cm}}^{{2}}\text {/V}\cdot \text {s}$ , a subthreshold swing of 260 mV/dec, and an ON/OFF current ratio of ~108 with negligible hysteresis voltage. The ZnO TFT shows excellent stability under bias stress because of the high-quality ZnO film and its excellent interface with ZrO x . The conduction band tail width of ZnO was obtained from the TCAD fitting to the measurement data and was found to be 65 meV.

Influence of Ce–W co-doping on phase transition temperature of VO2 thin films deposited by ultrasonic nebulized spray pyrolysis of aqueous combustion mixture

Vanadium dioxide is widely explored as a viable material for switching applications and a robust progress has been achieved on laboratory-scale. To realise its commercialisation, industrially-viable synthetic techniques are highly required. Ultrasonic nebulised spray pyrolysis of aqueous combustion mixture (UNSPACM) is a simple, low-cost and scalable technique which offers high quality films for various energy applications. Herein, we report synthesis, characterization and influence of Ce–W co-doping on phase transition temperature of VO2(M1) thin films deposited on quartz substrates at 350 °C by this technique. The phase was verified by x-ray diffraction and Raman spectroscopic studies. FTIR studies at 2.5 µm to 14 µm IR frequencies showed 63% reversible reflectance change of the films from low reflectivity below 60 °C to high reflectivity above 60 °C. Electrical resistance measurements on the thin films showed a first order transition with resistance change of three orders of magnitude. Ce-doping (2 atomic% of Ce) resulted in increase in reflectance (up to 72%) and transition temperature (up to 75 °C) while retaining strength of the transition. Ce–W co-doping lowered transition temperature (up to 67 °C) and reflectance (up to 45%) while retaining the transition strength. Ce–W co-doping also reduced surface roughness of the films up to rms roughness value of 36 ± 0.7 nm. We believe this technique provides an easy and simple means to synthesize VO2 thin films on large-scale for multiple applications such as smart windows among others.

Highly photoresponsive VO2(M1) thin films synthesized by DC reactive sputtering

We report synthesis, characterization and IR photoresponse properties of 150 ± 10 nm thick high quality VO2(M1) thin films synthesized by DC reactive sputtering. Phase formation was confirmed by X-ray diffraction and Raman spectroscopic measurements. Morphology and microstructure were analysed by atomic force microscope, scanning electron microscope and transmission electron microscope which revealed polycrystalline nature of nanosized films with root mean square (rms) roughness value of 8 ± 0.7 nm. Electrical measurements revealed 1st order transition of thin films with a change in resistance of more than two orders of magnitude and temperature coefficient of resistance, TCR of − 1.24% K−1 at 30 °C. The fabricated VO2(M1) IR photodetector exhibited excellent reproducible photoresponse properties when subjected to a 1064 nm laser under 250 mW cm−2 power density with a bias voltage of 5 V at the ambient conditions of temperature and pressure. The sensitivity, responsivity, external quantum efficiency and specific detectivity were observed to be 1775%, 40.09 mA W−1, 4.67% and 7.07 × 1011 Jones, respectively.

BCl3-Based Dry Etching of Exfoliated (100) ß-Ga2O3 Flakes

We report on BCl3-based dry etching characteristics of (100) β-Ga2O3 flakes using inductively coupled plasma etching technique, which were prepared by mechanical exfoliation from Ga2O3 single crystal. The etch rate of (100) Ga2O3 flake increased with increasing bias rf powers up to 52 nm min−1 using 25 sccm BCl3/15 sccm N2 gas chemistry. We also examined the etch rate dependence of Ga2O3 on crystal orientation. The (100) Ga2O3 flake has the lowest etch rate when compared with (010) and Ga2O3 surfaces. The lowest etch rate of (100) Ga2O3 surface results from less Ga-O bond breaking efficiency and low dangling bond density on the surface. It is notable that Ga2O3 surface is etched at higher rate than (010) and (100) Ga2O3 surfaces. The surface morphologies of etched (100) Ga2O3 surface exhibited little change, and rms roughness values remained less than 1.5 nm over a broad range of etch conditions.

The impact of ZnO configuration as an external layer on the sensitivity of a bi-layer coated polymer optical fiber probe.

Salinity magnitude changes are a critical factor for determining the chemistry of natural water bodies and biological processes. Label-free refractive index sensors are promising devices for detecting these changes. A polymer optical fiber (POF) sensor modified with cladding treatment and a bi-layer zinc oxide/silver (ZnO/Ag) nanostructure coating to determine sodium chloride concentration changes through refractive index variations in water is experimentally demonstrated. The use of three ZnO nanostructure shapes, nanoparticles and horizontally and vertically oriented nanorods, as an external layer and a broad spectrum light source from the visible (Vis) to the near infrared (NIR) region are investigated to achieve optimum sensitivity. The rms roughness, optical band-gap and zeta potential (ZP) value for the vertically oriented sample are 148 nm, 3.19 eV and 5.96 mV, respectively. In the NIR region the wavelength–intensity sensitivity values of probes coated with ZnO nanoparticles and horizontally and vertically oriented nanorods are 104 nm RIU−1–12 dB RIU−1, 63 nm RIU−1–10 dB RIU−1 and 146 nm RIU−1–22 dB RIU−1, respectively, and in the Vis area the values are 65 nm RIU−1–14 dB RIU−1, 58 nm RIU−1–11 dB RIU−1 and 89 nm RIU−1–23 dB RIU−1, respectively. The maximum amplitude sensitivity is obtained for the probe coated with vertically aligned ZnO nanorods in the NIR area due to the deeper penetration of evanescent waves, a higher surface-volume ratio, better crystallinity, more adhesive interactions with salt molecules, larger surface roughness and higher-order dispersion compared to the other coated ZnO nanostructures.

Fabrication of optical components using a consumer-grade lithographic printer.

The ability to 3D print optical elements will greatly expand the accessibility of optical fabrication. Here, we report on two fabrication techniques for plano-convex lens files using a consumer-grade lithographic printer. Lenses were post-processed using a simple spin coating technique with the resin used in the printing process or by curing directly on glass concave lenses. Average RMS roughness values were between 13 and 28 nm and RMS wavefront deviations were between 0.297 and 0.374 wave for spin-coated lenses. The average roughness RMS for the glass-cured lenses was 6 nm and the average form RMS was 0.048 wave.

Sintered Tape-cast 3YSZ Supports Human Bone Marrow Derived Stem Cell Osteogenic Differentiation

ABSTRACTSintered tape-cast yttria-stabilized zirconia (YSZ) was evaluated for its elemental composition, crystal structure, and imaged with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Human bone marrow stem cells (hBMSC) were cultured on the ceramic and differentiated into the osteoblast lineage; alkaline phosphatase (ALP) activity was tracked as a differentiation marker. The YSZ was composed of purely tetragonal grains with a median equivalent circular diameter of 283 nm. Zirconium, yttrium, oxygen, and adventitious carbon was detected on the substrate with no other elements in significant quantities detected. YSZ samples had an RMS roughness value of 27 nm, elastic modulus of 206 ± 14 GPa, and hardness of 14 ± 2 GPa. hBMSC were observed to attach and proliferate on the YSZ surfaces and had significantly increased ALP versus the undifferentiated control cultured on glass. This method for producing a YSZ ceramic yields a typical material of this type and supports attachment and differentiation of hBMSC; thus, making it useful as a bone implant material.

Epitaxial BaSnO3 and SrSnO3 perovskite growth on SrTiO3(001) via atomic layer deposition

The authors report epitaxial BaSnO3(001) and SrSnO3(001) growth on SrTiO3(001) (STO) substrates via atomic layer deposition (ALD) at 180 °C, where the BaSnO3 growth rate is 0.46 ± 0.03 Å and the SrSnO3 growth rate is 0.69 ± 0.04 Å per ALD unit cycle. Reflection high-energy electron diffraction, x-ray diffraction (XRD), and rocking curve analyses verify the single crystalline nature of BaSnO3(001) and SrSnO3(001) thin films on STO(001), while the atomic force microscopy analyses reveal the smooth surface of the stannate films with rms roughness values of ∼0.4 nm, which is only slightly higher than the STO substrate roughness of 0.32 nm. Out-of-plane XRD and reciprocal space mapping show that both BaSnO3(001) and SrSnO3(001) (∼10 nm) are fully relaxed on STO(001), owing to the large lattice mismatches (5.1% for BaSnO3/STO and 3.2% for SrSnO3/STO). The visible light transmittance spectra indicate that ALD-grown BaSnO3 and SrSnO3 thin films have high transparency at 400–800 nm that matches the transparency of STO(001) substrates.

Enhanced UV light induced photocatalytic degradation of Methyl Orange by Fe doped spray pyrolysis deposited ZnO thin films

ZnO and Fe doped ZnO thin films have been prepared by using simple homemade spray pyrolysis unit. The optimum temperature for the growth of thin films was found to be 300 ± 5 °C. The morphological, structural and optical properties were studied for these thin films. The X-ray diffractrograms exhibit hexagonal wurtzite crystal structure without any additional phase of the thin films. The root-like shapes (Ganglia) structure observed over the surface of the substrate by Scanning Electron Microscope (SEM). From UV–Vis diffuse reflectance spectroscopy (DRS) the band gap value of Fe doped films was found to be 3.92 eV. The peak shift in the Photo Luminance analysis confirms the presence of Fe content in the thin films and also there is a red shift. AFM images shows that RMS roughness value has decreases compared to pure ZnO films. The Photocatalytic activity of the prepared Fe doped thin films was evaluated using the Methyl Orange dye (MO) under UV light source. Nearly 89% dye degradation in 80 min was observed for Fe doped ZnO thin films.

Surface Characterization of Ion Implanted 4H-SiC Epitaxial Layers with Ion Energy and Concentration Variations

In this study, Al and N implantation effect on surface properties of 4H-SiC epitaxial layers were investigated before annealing process. AFM results indicated that all implanted samples indicated relatively low RMS roughness values. From UPS and XPS analysis, work function and Si-C binding energy of implanted samples were increased compared to the reference 4H-SiC sample. Those variations may be caused by lattice disorder and amorphization. In addition, TEM image showed damaged area in 4H-SiC epitaxial layer.

The impact of thickness on the optical, electrical and dielectric properties of nanocrystalline 0.9 MTO-0.1BNO composite thin films

Abstract The 0.9 MgTiO3–0.1Ba5Nb4O15 (0.9MTO-0.1BNO) thin films deposited on Pt (111)/TiO2/SiO2/Si (100) and SiO2 substrates by RF reactive magnetron sputtering have been reported. The films are deposited at a substrate temperature of 400 °C under 50/50 argon (Ar2)/oxygen (O2) mixed ambiance by varying the film thickness. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) studies have confirmed presence of both MTO and BNO phases.. The obtained strain in the films is found to be reduced with an increase in film thickness. The 3d crystal structure of MTO exhibited significant variations in bond length for the films with different thicknesses. The dispersion in the refractive index of the films has obtained using the single electronic oscillator model, and the obtained bandgap value is found to be reduced from 3.75 to 3.34 eV with an increase in film thickness from 150 to 340 nm, accordingly. The films revealed uniform spherical shaped particles with smooth surface with small rms roughness values around 2.9 to 2 nm. The microwave and low frequency dielectric responses showed improvment with an increase in film thickness. The impedance spectroscopy analysis displayed Cole-Cole behavior indicating the non-Debye conduction process present in the films. The frequency dependent conduction process has analyzed by Jonscher's Power law and the non-overlapping small polaron hopping nature has been observed. Extracted activation energies estimated from conductivity are found to be in the range of 0.31 eV to 0.14 eV. The leakage current density (J) with the applied potential has found to be in the range of 10−6 A/cm2 at 100 kV/cm2 for 340 nm film. The obtained results suggest that these films are promising for optical and microwave integrated circuit applications.

Analysis of the Effect of Soil Roughness in the Forward-Scattering Interference Pattern Using Second-Order Small Perturbation Method Simulations

Soil moisture (SM) is a key geophysical variable that can be estimated at regional scales using remote sensing techniques, by making use of the known relationship between soil reflectivity and the dielectric constant in the microwave regime. In this context, the exploitation of available illuminators of opportunity that currently emit large amounts of power at microwave frequencies (compared to typical synthetic aperture radar systems) is promising. Some published techniques estimate SM by analyzing the interference pattern (IP) between direct and reflected signal as measured by a single antenna (i.e., IP technique). In this letter, a new approach to simulate the IP is proposed, in which the soil roughness is modeled straightforwardly using the second-order small perturbation model. Results illustrate that the “notch” in the VV-polarization IP (related to the Brewster angle) can only be directly observed for very low values of soil rms roughness ( $s cm). For typical values of soil roughness ( $s\sim 1.2$ cm), the notch disappears and only a minimum in the IP is observed near the Brewster angle.

Exploration of surface plasmon resonance for sensing copper ion based on nanocrystalline cellulose-modified thin film.

In this research, surface plasmon resonance (SPR) spectroscopy was used for sensing copper ion by combining the SPR with nanocrystalline cellulose modified by hexadecyltrimethylammonium bromide and graphene oxide composite (CTA-NCC/GO) thin film. The binding of Cu2+ on CTA-NCC/GO thin film was monitored by using SPR spectroscopy. By using the obtained SPR curve, detection range, binding affinity, sensitivity, full width at half maximum (FWHM), data accuracy (DA), and signal-to-noise ratio (SNR) have been calculated. The results showed that the sensor detection range was 0.01 until 0.5 ppm, and that it reached a saturation value. Moreover, the resonance angle shift followed the Langmuir isotherm model with a binding affinity constant of 4.075 × 103 M-1. A high sensitivity of 3.271° ppm-1 also was obtained for low Cu2+ concentration ranged from 0.01 to 0.1 ppm. For the FWHM, the lowest value calculated was at 0.08 and 0.1 ppm, which is 3.35°. The DA of the SPR signal consecutively highest at 0.08 and 0.1 ppm. Besides that, the SNR of the SPR signal increases with the Cu2+ concentrations. The CTA-NCC/GO thin film morphological properties were also studied by using atomic force microscopy. The rms roughness values, which were obtained before and after in contact with Cu2+, were 3.51 nm and 2.46 nm, respectively.

Preparation and Characterization of Flexible, Transparent and Thermally Stable Aromatic Co-polyamides

Two aromatic co-polyamides were synthesized combining two diacid monomers containing bulky pendant groups, 5-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)isophthalic acid (DEAIA) and 5-tert-butylisophthalic acid (TERT), with 4,4′-(hexafluoroisopropylidene)dianiline (HFA) or 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) by direct polycondensation. The structures of the obtained aromatic co-polyamides were confirmed by FTIR, Raman and 1H-NMR. The co-copolyamide films, DHTH and DDTD, exhibited rms-roughness values between 0.94 and 1.60 nm, respectively. Moreover, they presented good thermal stability up to 300 °C. Young’s moduli of the co-polyamide films were between 4.1 and 4.3 GPa. X-ray diffraction results showed that the co-polyamide films were amorphous due to the incorporation of both bulky pendant groups, tert-butyl and dibenzobarrelene. The combination of bulky pendant groups provided intrinsically transparent co-polyamide films with a transmittance higher than 88% in the range of 400−780 nm. Due to these outstanding film and optical properties, they are suggested to be flexible substrates in applications for solar cell and other portable electronic devices.

Influence of compositional variation on the optical and morphological properties of Ge[sbnd]Sb[sbnd]Se films for optoelectronics application

Thin films of GexSb40-xSe60 (x = 15, 20, 25, 27, 32 and 35 at.%) were deposited on quartz by vacuum thermal evaporation of the pre-synthesized parental glasses powders. By spectroscopic ellipsometry the complex refractive index values are determined in the 0.20–33 μm spectral range. The optical band gap and single oscillator energies are established as a function of the Ge content and average coordination number Z. In the (0.85–3.5) μm spectral range the GexSb40-xSe60 films possess about 80% transmission. Infrared ellipsometric and Raman studies identified SeSe and GeGe homopolar bonds, oxygen and hydrogen related impurity bonds and heteropolar GeSe and SbSe chemical bonds. Neutron- and X-ray Diffraction data coupled with Reverse Monte Carlo simulations support the optical results reproducing the GeSe and SbSe cell units and cross-linked GeGe bonds. Atomic force microscopic imaging confirmed smooth surfaces with low RMS roughness values (<2.3 nm) and continuous structure of grains of (16–22) nm diameters. All the considered material parameters show peculiarities in the compositional dependences around 27 at.% Ge, corresponding to average coordination number Z = 2.67, testifying structural phase transition at high Ge content in the GexSb40-xSe60 films.

Chemical Mechanical Polishing and Direct Bonding of YAG

Current limitations in both single crystal and polycrystalline (ceramic) solid state laser technologies for high power applications stem from thermal effects that cause degradation in both lasing efficiency and beam quality. YAG and Y2O3 have favorable material properties for producing these high power lasers. We demonstrate chemical mechanical polishing (CMP) processes for YAG and Y2O3 resulting in smooth surfaces, (< 1 nm RMS roughness), defect free, and subsequently suitable for direct bonding. The CMP process has been used in conjunction with surface activation to form single crystal YAG-YAG and polycrystalline Y2O3-Y2O3 bonded elements showing a proof of concept for the fabrication of composite laser elements. YAG single crystals were successfully polished with a 70-nm colloidal silica solution containing NaOH (pH 9.9). X-ray photoelectron spectroscopy measurements provided insights to the chemical impact of the NaOH. After NaOH exposure, YAG showed complete removal of Al from tetrahedral sites and a change in the Y3/2 and Y5/2 peak area ratios, indicating that the surface of YAG was sufficiently modified to allow the silica particles to abrade the byproduct surface layer. The final surface roughness after polishing was measured at 0.1 nm RMS roughness with no scratches deeper than 0.3 nm. YAG single crystals were also polished with a 70-nm Al2O3 slurry containing NaOCl (pH 11.4), however AFM measurements showed that the surface produced, 0.5 nm RMS roughness with no scratches deeper than 6.0 nm, was not as good as polishing with the colloidal silica slurry which was attributed to the effect of the chemical action of NaOH with the YAG surface. Polishing polycrystalline Y2O3 required a slurry with less aggressive chemical reactions, so the NaOCl/Al2O3 slurry was used to successfully polish the substrates to RMS roughness values of 0.5 nm and scratches no deeper than 1.0 nm. Triple axis diffraction rocking curves and double crystal x-ray diffraction imaging were used to demonstrate that the CMP process also removed subsurface damage that was present in the as-supplied material. The triple axis technique was also successfully employed for the first time to demonstrate that the polycrystalline Y2O3 subsurface damage was also significant reduced after the CMP process. After CMP and surface treatment, YAG-YAG and Y2O3-Y2O3 were bonded together and annealed at 1425 °C with no applied pressure. Cross section and plan view high resolution transmission electron images of the YAG-YAG bonded interface revealed a defect free bonding interface. Light transmission measurements showed that 90% of the interface area was bonded at room temperature contact and was further strengthened with annealing at 1425 °C for 72 hours. These conditions possess a much lower thermal budget than those previously shown to be required to bond YAG without a CMP step. The CMP and surface treatment processes that have been developed are applicable towards the creation of solid state laser composite elements and enable further progress and development for high power laser applications.

PREPARATION OF POLY (METHYL METHACRYLATE) THIN FILMS BY SPIN COATING TECHNIQUE FOR OTFT AND WOUND HEALING APPLICATIONS

Thin films of poly (methyl methacrylate) (PMMA) were prepared on cleaned glass slides by using spin coating technique. The prepared films were identified by using FTIR spectrum. Surface morphology of the coated films was studied by using SEM and AFM. Both as grown and annealed films showed smooth and amorphous structure. It also revealed the absence of pits, pin holes and dendritic features in the surface. Both as grown and annealed films showed very low RMS roughness value. The morphology analysis revealed that the prepared film could be used as dielectric layer in thin film transistors and as drug delivery system forwound healing.

Silicon-doping influence on the crystalline, surface and optical features of cadmium oxide films deposited by sol-gel spin route

This is the first study on Si-contributed CdO films fabricated via sol-gel process. Si-doping impact on the crystalline, topographic and optical qualities of cadmium oxide has been searched with XRD, SEM, AFM and UV/vis spectrophotometer. The whole films were polycrystalline with (111) preferential direction and the crystalline degree of CdO depended on Si-contribution effect. The crystallite size of undoped-CdO incessantly decreased with Si-content, however dislocation density increased with Si-level. The spherical CdO granules were nanoscale and their sizes varied between 20–170 nm. The RMS roughness values of films changed between 5.84 nm–40.5 nm. The optical gap value of undoped-CdO continuously declined from 2.59 eV to 2.39 eV with increasing Si-content, while the Urbach energy increased from 350 meV to 468 meV with Si-level. These results reveal that the level of Si-doping affect the features of cadmium oxide.

Nickel doping effect on properties of sprayed In2S3 films

Nickel doped In2S3 films have been prepared by the chemical spray pyrolysis technique at 350 °C on glass substrates. The Ni doping level was changed by varying Ni:In molar ratio from 0 to 4% in solution. The structural studies reveal that the Ni-doped In2S3 films are polycrystalline and exhibit a cubic structure. As the Ni:In molar ratio increases, the crystallite size decreases from 27.5 to 23 nm and RMS roughness values increase from 12 to 18 nm, respectively. The presence of Ni in the deposited films was confirmed by energy dispersive spectroscopy. Raman studies show different peaks related to In2S3 phase and do not reveal any secondary phases of In–Ni and Ni–S. The transmission coefficient is about 70–55% in the visible region and 85–75% in near-infrared region. The band gap energy increases from 2.66 to 2.82 eV for direct transitions with the increase of Ni:In ratio from 0 to 4%. The refractive index values of In2S3:Ni thin films decrease from 2.46 to 2.40 and the extinction coefficient values are in the range 0.01–0.20.

The effect of Eu-loading on the some physical features of CdO

The Eu-loaded CdO thin films were coated on the glass substrates with a sol-gel spin coating method by using Cd(CH3COO)2·2H2O and EuCl3·6H2O salts. The effect of Eu-loading ratio varied from 0 to 4at% in the step of 1at% on the structural, morphological, electrical, and optical features of cadmium oxide had been evaluated with XRD, Raman study, SEM, AFM, Four Point Probe, and UV/VIS analysis. The coated films were polycrystalline with (111) preferential orientation and they had a cubic cadmium oxide structure. The granular-structure was observed from SEM and AFM images. The sizes of granules were in the range of 15–220nm. It was observed that the homogeneity of granule distribution deteriorated with Eu-content. The RMS roughness value increased from 4.1nm to 284nm with Eu-doping. The minimum sheet resistance was found to be 4.8 × 102Ω for 2at% Eu-content, but the maximum optical band gap was determined to be 2.61eV for 1at% Eu-content. The Urbach energy varied between 366meV and 658meV. As a result of this work, Eu-doping has an important effect on the properties of cadmium oxide.