Glancing Angle Deposition Technique Research Articles

Self-cleaning structural colors by TiO2/Ti nanostructures.

Structural colors are fascinating due to their stability in comparison with dyes and pigments; nevertheless, environmental pollutants contaminate surfaces and redefine structural colors. To overcome this problem, cleaning of the surface is necessary at regular intervals, which is cumbersome and costly. We have circumvented this issue in this article and fabricated scalable self-cleaning structural colors. The structural colors are generated by TiO2 nanorods and thin films on Ti sputtered glass and flexible polyethylene terephthalate substrates employing a glancing angle deposition (GLAD) technique. Theoretical calculations based on thin film interference validate the experimental results and suggest Al, Ni, Co, and Cu as an alternative of Ti for generating structural colors. Structural colors are transformed to a superhydrophilic state, i.e., a self-cleaning state, via UV exposure and annealing at elevated temperatures. In addition to a self-cleaning state, annealing could control the opaqueness and color tunability of the structural colors. A permanent wettability state in between the superhydrophobic and superhydrophilic states of the structural colors is controlled by the GLAD technique. Moreover, the structural colors are demonstrated for information encryption and optical ethanol sensing applications.

Portable and sensitive Ag nanorods based SERS platform for rapid HIV-1 detection and tropism determination

In this study, surface-enhanced Raman scattering (SERS) based field-deployable platform has been explored for early detection and distinction of the human immunodeficiency virus (HIV-1). A highly optimized silver nanorods array, fabricated using glancing angle deposition technique was used as SERS substrate. Distinct signature peaks for varying concentrations (102 to 106 copies/mL) were identified in five different HIV-1 subtypes (A, B, C, D, and CRF02_AG). Binding of viruses directly with Ag nanorods without using antibodies or intermediate reagents is shown. The purified viruses were spiked in water and healthy plasma to capture pure HIV-1 peaks. Distinct peaks were also captured for the X4 and R5 tropic strains suggesting tropism based detection. The above data was further confirmed and analyzed statistically using a multivariate tool. Thus, the present study indicates the ability of the SERS platform to detect and differentiate the HIV-1 virus implying its further validation using clinical specimens and isolates.

Investigating the effect of silver nanorods embedded in polydimethylsiloxane matrix using nanoindentation and its use for flexible electronics

AbstractThe stretchable electrodes with excellent flexibility, electrical conductivity, and mechanical durability are the most fundamental components in the emerging and exciting field of flexible electronics. This article proposes a method for fabrication of such a stretchable electrode by embedding silver nanorods (AgNRs) into a polydimethylsiloxane (PDMS) matrix that is grown by a unique glancing angle deposition technique. The surface, mechanical, and electrical properties of PDMS are significantly changed after embedding the AgNRs in it. The results show that surface roughness and polarity increase after AgNRs are embedded in the PDMS matrix. Elastic modulus (E) and hardness (H) decrease with an increase in the indentation load as a result of the indentation depth effect. Due to strong interfacial adhesion of AgNRs embedded in the PDMS matrix, the E and H of nanocomposite are increased by 167.6 and 93.3% compared with PDMS film, respectively. Furthermore, the AgNRs‐PDMS film has an electrical resistivity value in the order of 10−7 Ωm. It remains conductive during various mechanical strains such as bending, twisting, and stretching, which is demonstrated using a light‐emitting diode circuit. Simultaneously, the antimicrobial activity of silver could make it a promising candidate for wearable electronics.

Post deposition annealing effect on the electrical properties of β-Ga2O3 Nanowire

This study reports the fabrication of vertically aligned β-Ga2O3 nanowires over the silicon substrate by the glancing angle deposition technique. Thermal annealing was done to the fabricated sample in ambient atmospheric conditions at 900 °C for 1 h. The annealed sample shows a higher average crystallite size (20.19 nm) when equated to the as-deposited one (13.72 nm). The annealed sample also shows a lower turn-on voltage of + 2.5 V. A maximum responsivity of 152.34 A/W and an internal gain of 675.02 were obtained for the annealed device at 260 nm. Low noise equivalent power (8.4 × 10–14 W) and high sensitivity towards light were observed for the annealed device which makes it a promising contender for optoelectronics device application.

Opto-electrical characterization of quaternary sputtered copper indium gallium selenide nanorods via glancing angle deposition

Nanorod arrays have become an attractive alternative to their thin film and bulk counterparts in photovoltaic and photoconductivity research. This is mainly attributed to their superior optical and electrical properties. Light trapping and unique bandgap geometries in vertically aligned nanostructures result in high optical absorption and provide enhanced carrier collection by utilizing a fully depleted p-n junction between the anode and cathode via an isolated “capping” construction. The combination of these two features leads to the development of high efficiency nanostructured devices that can be utilized in solar cells and photodetectors. Optical absorption properties, geometry, and opto-electrical properties of nanorod arrays of CuInxGa(1−x)Se2 (CIGS), a p-type semiconductor with a wide bandgap ranging from 1.0 to 1.7 eV, are compared to their thin film counterparts. Utilizing a radio frequency sputtering system, a quaternary target, and glancing angle deposition technique, both isolated vertical arrays of CIGS nanorods and “core-shell” devices were fabricated, while conventional film devices were fabricated by normal incidence deposition. Scanning electron microscopy images indicated a successful growth of CIGS nanorods. Optical absorption and opto-electrical performance were found to be strongly improved by the presence of the isolated nanorod structures through spectroscopic reflectometry and responsivity testing under a solar simulator.

Annealed n-TiO2/In2O3 nanowire metal-insulator-semiconductor for highly photosensitive low-noise ultraviolet photodetector

Superior performance by annealed TiO2/In2O3 nanowire (NW) metal-insulator-semiconductor device, synthesized using electron beam evaporation incorporating catalytic free glancing angle deposition technique. TiO2/In2O3 NW annealed at 600 °C showed 15,000 times photosensitivity enhancement under wavelength 330 nm illumination at −5 V as compared to as-deposited TiO2/In2O3 NW. TiO2/In2O3 NW annealed at 600 °C exhibits high responsivity and quantum efficiency of 325 A/W and 1,20,000 respectively at 330 nm. Further, it exhibited low noise-equivalent power of 9.62 × 10−17 W and high detectivity of 2.91 × 1016 Jones with fast photoresponse speed of 0.2622 s and 0.1334 s rise and fall time respectively. This superlative performance of TiO2/In2O3 NW heterostructure annealed at 600 °C gives the path for proficient optoelectronics UV photodetection applications.

Scrutinizing and Collating the Broadband Photo-Detection Properties of Isotype n-MnO₂/TiO₂ Nanostructure

Fabrication of heterostructure MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film (TF) and MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanowires (NW) has been carried out using Glancing angle deposition technique. The X-ray diffraction pattern revealed MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are crystalline, while TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are amorphous in nature. Formation of the vertically aligned NW can further be verified from field emission gun scanning electron microscopy. The fabricated NW shows 15-fold enhancement in UV-Vis absorption. Detectivity was found out to be 9.9 × 1010 Jones and 1.95 × 1012 Jones for MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TF and MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW respectively. The calculated NEP is 4.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> W for MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TF and 2.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> W for MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW. This indicates the overall improved noise performance by MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ITiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NW. The rise and fall time of NW are 0.21 s and 0.50 s respectively, which is faster compared to 0.29 s and 0.64 s of TF. In overall, NWs shows great performance as compared to TF and has a great potential in applications of uv-vis range photodetector.

Influence of an Annealing Temperature in a Vacuum Atmosphere on the Physical Properties of Indium Tin Oxide Nanorod Films.

In the present study, indium tin oxide (ITO) nanorod films were produced by usage of ion-assisted electron-beam evaporation with a glancing angle deposition technique. The as-produced ITO nanorod films were annealed in the temperature range of 100-500 °C for two hours in a vacuum atmosphere. The as-produced ITO nanorod films exhibited (222) and (611) preferred orientations from the X-ray diffraction pattern. After vacuum annealing at 500 °C, the ITO nanorod films demonstrated many preferred orientations and the improvement of film crystallinity. The sheet resistance of the as-produced ITO nanorod films was 11.92 Ω/ and was found to be 13.63 Ω/ by annealing at 500 °C. The as-produced and annealed ITO nanorod films had a rod diameter of around 80 nm and transmittance in a visible zone of around 90%. The root mean square roughness of the as-produced ITO nanorod film's surface was 5.49 nm, which increased to 13.77 nm at an annealing temperature of 500 °C. The contact angle of the as-produced ITO nanorod films was 110.9° and increased to 116.5° after annealing at 500 °C.

Highly improved responsivity of self-powered UV–Visible photodetector based on TiO2/Ag/TiO2 multilayer deposited by GLAD technique: Effects of oriented columns and nano-sculptured surface

The outstanding progress made in optoelectronic technologies calls for a renewed performance assessment of photodetectors (PDs) for next-generation sensing applications. Here, TiO2/Ag/TiO2 tri-layered films were sputtered using the GLancing Angle Deposition (GLAD) technique in which the deposition angle was varied from 0 to 80°. Before the elaboration, a strategic combination of Genetic Algorithm (GA) and numerical analysis was used to find out the best multilayer geometry offering superior optical performance. The influence of the inclined architecture on the performance of the prepared TiO2/Ag/TiO2 multilayer was analyzed. Optical characterization reveals that near-perfect UV photodetection and over than 60% of visible-absorbance were achieved by taking a deposition angle of 80°. These enhancements are correlated to the surface nano-sculptured structures, which gives rise to an enhanced light-trapping capability. The measured I-V curves of the obliquely-deposited structures showed a clear photovoltaic mode and an extremely low dark current of a few picoamperes. Besides, the devices demonstrate an enhanced self-powered UV–Vis photoresponse, yielding superb UV and visible responsivity of 0.2A/W and 47 mA/W, respectively. The UV, blue, and green current ratios were respectively 137, 113, and 107 dB. Therefore, promoting efficient light management, this innovative concept of inclined tri-layer films provides a sound pathway for designing potential alternative self-powered UV–Vis PDs appropriate for the future development of the optoelectronic technology.

Tuning the optical properties of SnO2/Ag/SnO2 tri-layers by changing Ag thickness

In this work, for the first time, the effect of changing Ag thickness on the optical and electrical properties of SnO2/Ag/SnO2 tri-layered films prepared by magnetron sputtering equipped with glancing angle deposition has been investigated. Several parameters such as figure of merit (FOM), sheet resistance, NIR emissivity, and refractive index have been studied for the structure prepared by the different thickness of Ag. It has been found that the sample with thickness of 100 and 25 nm, respectively, for the SnO2 and the Ag layers has the maximum FOM of 44.37 × 10−4 Ω−1, the sheet resistance of 7.53 Ω/sq, average transmittance of 71.18% and NIR emissivity of 0.093 which shows the remarkable impact of the glancing angle deposition technique on the optical and electrical parameters of these structures.

Self-sustainable and recyclable Ag nanorods for developing Ag-Ag2S nano heterostructures using sewage gas: Applications in photocatalytic water purification, hydrogen evolution, SERS and antibacterial activity

Multifunctionality and recyclability of Ag nanorods array (well known tas potential SERS substrates) have been explored for other imperative applications like water purification by photocatalytic dye degradation, hydrogen evolution, antibacterial activity, and SERS based detection after sulfurization. An easy and green approach of exposing the Ag nanorods array to sewage H2S gas has been applied for sulfurization. This resulted in multifunctional Ag-Ag2S nanoheterostructures manifesting a metal-semiconductor heterojunction with exceptional optical, electronic and photocatalytic properties. The Ag nanorods array on glass as well as ITO substrates were fabricated by glancing angle deposition technique and then sulfurized by exposing to a sewage site, resulting in Ag-Ag2S nanoheterostructures at ambient conditions and confirmed by several morphological, structural and elemental characterization tools. The fabricated nanoheterostructures are utilized efficiently for important applications including dye degradation under visible light irradiation within 30 min, photoelectrochemical reaction for hydrogen evolution, surface enhanced Raman scattering based detection and significant bactericidal effect. The salient features of synthesized Ag-Ag2S nano-heterostructures comprise an important self-sustainable approach which is pivotal in the present research scenario that requires significant multidimensional applications.

Effects of substrates on the crystalline growth and UV photosensitivity of glancing angle deposited porous ZnO nanostructures

We prepared ZnO nanostructures on three different substrates such as quartz, sapphire (Al2O3) (001) and MgO (100) by glancing angle deposition (GLAD) technique using KrF excimer pulsed laser and investigated the effects of various substrates on the growth and optical properties. The GLAD technique promotes a vertical growth of the nanostructures and hence creates necessary porosity for penetration of light through the top of the surface. Although these nanostructures are porous, they are highly crystalline and oriented along c-axis of the wurtzite structure. Notably, despite the amorphous nature of the quartz substrate, nanostructures on quartz are preferentially oriented towards the c-axis. All three samples show intense ultraviolet (UV) emission with a highly suppressed visible emission, where the suppression depends on the growth and porous morphology of nanostructures. The variation in morphology and the porosity strongly influenced the electrical properties and UV photo-detection of these nanostructures when exposed under UV (254 nm) light. Although we used the same technique of the growth, the lowest dark current (0.14 nA) with the highest UV photosensitivity (182 %) is achieved for the highly porous and yet crystalline nanostructures grown on the sapphire substrate. Generally, it is extremely difficult to maintain crystalline structure with porosity; however, here we demonstrate a promising approach in designing visible-blind photodetectors by combining these two opposites, porosity and crystallinity, in ZnO nanostructures using the GLAD-assisted pulsed laser deposition method.

Annealing Effect of Glancing Angle Electron Beam Deposited TiO2/In2O3 Nanowires Array on Surface Wettability

TiO2/In2O3 nanowire (NW) array are prepared using catalyst free glancing angle deposition technique. The wettability of TiO2/In2O3 NW surface are tuned and controlled by the annealing treatment without altering the surface with additional chemical coating. The phase change, surface roughness, change in static and dynamic contact angles due to the heat treatment are studied. Moreover, the surface properties such as frictional force and work of adhesion are calculated for all the samples. The samples annealed at 600 °C shows nearly superhydrophilic with static water contact angle of 12°, frictional force of 85.00748 µN and work of adhesion of 142.3721 mN/m. The surface of TiO2/In2O3 NW is controlled to attain desired water contact angles and sliding angles, which is paramount for designing practical application in self-cleaning, electronic and biomedical fields.

Effect of Annealing on Morphology and Photoluminescence of WO₃ Nanowires Deposited by Glancing Angle Deposition Techniques.

In this article, vertically aligned WO₃ nanowires were synthesized by employing the glancing angle deposition technique. The significant improvement in the crystallinity and surface morphology of the synthesized WO₃ nanowires were observed for 500 °C annealed samples and beyond that temperature it starts degrading. The X-ray diffraction confirmed the different phase transition after annealing. Increase in crystallite size from 68.93 nm to 77.41 nm was observed with the increase in annealing temperature from 300 °C to 500 °C. Upon 250 nm excitation, a broad blue emission aroused by near band edge emission is observed. Also, other emission peaks were observed due to the localized states of oxygen vacancies in the conduction band of WO₃. Fourier transform infrared result shows the bonding of WO₃ nanowires and intensity were greatly enhanced as the annealing temperature increases up to 500 °C. These enhancements in the properties could be applicable for the development of WO₃ based nanodevices.

(Invited) Trace Level Detections By Surface-Enhanced Raman Scattering

The Raman signals of molecules attached on the very surface of noble metals nanostructures can be greatly enhanced due to the enhancement of the local electric field, by the localized surface plasmon resonance of the nanostructures incident by the laser beam. Therefore, one can make Raman scattering a powerful means in recognizing and quantifying molecules at trace levels. This, however, relies on the sensitivity, stability, etc., of the nanostructures which are used as the substrate surface-enhanced Raman scattering (SERS), and also, the methodologies to quantify the molecules, which are quite difficult even for normal Raman scattering.We report here, our attempts to design and fabricate silver nano rods as substrate for surface-enhanced Raman scattering, with very high sensitivity, thermal and chemical stability, excellent reusability, etc., by glancing angle deposition techniques with an e-bam system, and covering the surface of the silver nano rods completely by atomic layers deposition of Al2O3 with a thickness of ~ 1.0 nm. These nanorods could be thermally stable in morphology and performance as the SERS substrates up to higher than 400 oC, and chemically stable in harsh environments. These makes the covered Ag nanorods applicable in real environments as SERS substrates. based on the principle component analysis (PCA), we also developed qualitative and quantitative analysis methodologies to quantify chemicals or molecules in complex systems even at trace levels by SERS. Several examples will be shown for trace level analysis of real samples by surface-enahnced Raman scattering with the substrates we designed and fabricated and the approaches we established.

Copper Oxide Thin Films for Sub-Ppm Acetone Detection Obtained By Glancing Angle Magnetron Sputtering Deposition

IntroductionThe number of gas-sensing applications increases year by year including industrial application as well as new approaches such as medical diagnostics, where gas sensors are used for measurement of volatile organic compounds present in the exhaled human breath. Over 3500 various VOCs have been already detected in the exhaled human breath, and a single breath consists of 500 various VOCs [1]. Apart from the conventional breath alcohol detectors, the novel applications appeared such as the detection of biomarkers [2]. One of the promising compounds that can be used as a biomarker is acetone, which is considered to be the biomarker of diabetes since people with diabetes tend to have higher acetone detection that healthy people [3,4]. The exhaled acetone is usually in the range of 0.2 - 0.8 ppm and over 2.5 ppm for people without and with diabetes, respectively. In order to measure such low, sub-ppm, concentrations, laboratory systems are applied including GC-MS [5], PTR-MS [6], and recently e-noses [7] as well as single sensors [8].In this paper, the investigation results on the copper oxide (CuO) deposited by utilization of magnetron sputtering technology with glancing angle technique are presented, where CuO was deposited at various parameters such as deposition angle, argon/oxygen ratio. The responses to various sub-ppm acetone concentrations are presented.CuO depositionThe gas-sensing applications of CuO have been previously confirmed and described [9]. Here, the CuO thin films were deposited by the UHV magnetron sputtering system from Kurt J. Lesker with a glancing angle deposition technique realized by utilization of a commercial ECR manipulator, which allows us to change the deposition angle, substrate rotation, and it has integrated heater that can be heated up to 850oC. The base vacuum pressure and deposition vacuum pressure were 0.001 Pa and 0.3 Pa, respectively. The temperature was fixed at 200oC, the power at 100W, the argon/oxygen ratios were 33%, 50%, 66%, 80% and 100% (pure oxygen without argon). After deposition, the samples were annealed at 400oC for 4 hours in the air. Gas-sensing measurements The developed sensors were tested in the dedicated measurement setup based on the quartz-tube oven with gas-dosing lines, where various target gas concentrations are obtained by utilization of mass flow controllers 1179B (MKS Instruments, USA) and acetone canisters with 5 ppm of acetone (Air Products, UK). The gas sensor response (S) was defined as resistance ratio S=(Rgas-Rair)/Rair, where Rgas and Rair are electrical resistances in gas and air, respectively. Results and Conclusions The sensors have been measured under exposure to acetone in the 0.25–2.5 ppm range, which covers the exhaled acetone range. The results have confirmed the influence of the glancing angle deposition for gas detection, in this case for acetone detection. The highest responses have been obtained for samples deposited at 85o (Fig.1b), however, the SEM verification will be carried out to compare the morphology and nanorods distribution. Moreover, the deposition system allows us to deposit the copper oxides at various argon/oxygen concentrations including deposition in pure oxygen. The results presented in Fig.1a shows, that the highest responses have been obtained for samples deposited at 20%/80% Ar/O2 ratio. It has been underlined, that the samples were annealed after deposition and preheated for 4h at 300oC, 350oC, and 400oC before the measurements. Further investigations are focused on choosing the optimal deposition conditions for acetone-sensors as well as long-term stability tests are performing.Fig.1. The sensors’ responses under exposure to acetone in the 0.25–2.5 ppm range at various operating temperatures for gas-sensing layer deposited at various (a) oxygen concentrations; (b) deposition angles. Acknowledgments This research was funded by the National Science Centre, Poland 2017/26/D/ST7/00355.

Boosted photoresponsivity using silver nanoparticle decorated TiO2 nanowire/reduced graphene oxide thin-film heterostructure

Here, we report on the fabrication and use of a silver (Ag) nanoparticle (NP) decorated TiO2 nanowire (NW)/reduced graphene oxide (RGO) thin-film (TF) heterostructure as a UV detector, using a controlled method called the glancing angle deposition technique. Transmission electron microscope images show Ag NPs (size 7–13 nm) covering the entire surface of the TiO2 NWs. A high absorption as well as photoluminescence for the Ag NP-TiO2 NW/RGO TF sample reveals the generation of a large number of electron–hole pairs compared to bare TiO2 NW. The resulting plasmonic UV photodetector from the Ag NP-TiO2 NW/RGO TF exhibits a rectification ratio of 5039 (+10 V) and responsivity of 1760 A W−1 at 350 nm light (with power density as low as 0.58 µW cm−2). Moreover, the device shows fast response speed (rise time of 157 ms and fall time of 488 ms) with detectivity and noise equivalent power of 6.659 × 1013 Jones and 51 fW, respectively. The enhanced plasmonic field and high scattering of light, along with the high mobility RGO layer at the bottom, result in the superior performance of the device.

Structure and optical properties of the WO3 thin films deposited by the GLAD magnetron sputtering technique

The deposition process and investigation of the physical properties of tungsten trioxide (WO3) thin films are presented in this paper. The WO3 thin films were deposited by magnetron sputtering technology with glancing angle deposition technique (GLAD) in a reactive mode. The substrate tilt angle various from 45° to 90° and 0°, and the sample rotation at a speed of 20 rpm was stabilized by the GLAD manipulator. After deposition, the samples were annealed at 400 °C/4h in air. Thin WO3 films were deposited on glass, quartz and silicon substrate. The crystal structure, morphology, and optical properties were determined by several x-ray measurements, optical spectroscopy, and spectroscopic ellipsometry. The structural and optical properties of the deposited films are presented and discussed.

GLAD Magnetron Sputtered Ultra-Thin Copper Oxide Films for Gas-Sensing Application

Copper oxide (CuO) ultra-thin films were obtained using magnetron sputtering technology with glancing angle deposition technique (GLAD) in a reactive mode by sputtering copper target in pure argon. The substrate tilt angle varied from 45 to 85° and 0°, and the sample rotation at a speed of 20 rpm was stabilized by the GLAD manipulator. After deposition, the films were annealed at 400 °C/4 h in air. The CuO ultra-thin film structure, morphology, and optical properties were assessed by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray reflectivity (XRR), and optical spectroscopy. The thickness of the films was measured post-process using a profilometer. The obtained copper oxide structures were also investigated as gas-sensitive materials after exposure to acetone in the sub-ppm range. After deposition, gas-sensing measurements were performed at 300, 350, and 400 °C and 50% relative humidity (RH) level. We found that the sensitivity of the device is related to the thickness of CuO thin films, whereas the best results are obtained with an 8 nm thick sample.

Non-volatile memory application of glancing angle deposition synthesized Er2O3 capped SnO2 nanostructures

An Er2O3 capped SnO2 nanostructure (NS) based memory device was synthesized on Si substrate by glancing angle deposition technique. Field emission scanning electron microscopy and transmission electron microscopy were used to verify the formation of the Er2O3 capped SnO2 NS. The Er2O3 capped SnO2 NSs were polycrystalline in nature as obtained from selected area electron diffraction analysis. Au metal contact was deposited over the Er2O3 capped SnO2 NS to fabricate a Au/Er2O3–SnO2/Si memory device. The Er2O3 capped SnO2 memory device showed a higher memory window of 1V, and higher charge storage capability (0.7 × 1010 cm−2) compared to a bare SnO2 NW memory device. The Er2O3 capped SnO2 device also exhibited good endurance over 500 programming/erasing cycles as well as good retention properties (measured for 103s) with charge loss as low as 1.86%. The programme/erase process of the Er2O3 capped SnO2 device is explained with respect to a band diagram. The fabricated Er2O3 capped SnO2 NS is a Type-II heterostructure with Er2O3 acting as a charge trapping layer. Such a heterostructure type is a good candidate for non-volatile memory applications.