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Effect of porous silicon substrate on structural, mechanical and optical properties of MOCVD and ALD ruthenium oxide nanolayers
摘要： Ruthenium oxide (RuO2) has received significant attention in recent years for its photocatalytic properties and photoelectrochemical (PEC) performance. In the present research, RuO2 nanolayers were grown on n-type porous silicon (PSi) by metal organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). The morphology, mechanical and optical properties of produced nanostructures were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, diffuse reflectance and photoluminescence (PL) spectroscopy. It was shown that that MOCVD gives non-uniform distribution of RuO2 along the pore and it is deposited mainly in the near-surface of PSi, while distribution of ruthenium obtained by ALD looks conformal over the entire pore. The mean size of RuO2 nanocrystallites and mechanical stresses were determined by TEM, XRD and Raman spectroscopy. It was demonstrated that samples obtained by ALD demonstrate a good crystallinity, while crystalline phase for samples produced by MOCVD improve with RuO2 layer thickness increasing. It was established the formation of hydrated RuO2 during ALD and MOCVD. It was shown that the samples produced by MOCVD have slightly higher electrical conductivity than ALD samples. The average value of energy gap (Eg) for samples prepared by MOCVD depended on the number of injections. RuO2 nanolayers quenched intrinsic PL from the PSi matrix. The correlation between structural, optical, and mechanical properties of samples produced by MOCVD and ALD was discussed.
关键词： MOCVD.,ruthenium oxide,ALD,porous silicon
更新于2025-09-10 09:29:36
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Optoelectronic attenuation behavior of Al2O3/ZnO nanolaminates grown by Atomic Layer Deposition
摘要： Zinc oxide (ZnO) and aluminum oxide (Al2O3) nanolaminates deposited in a homemade Atomic Layer Deposition (ALD) system are presented. In this work, three samples with a multi-films structure formed by four Al2O3/ZnO bi-layers of 20 nm were synthetized by thermal ALD. To analyze the optoelectronic response, the thickness of the Al2O3 was varied at 1%, 3% and 5 % of the total bi-layer width for each sample. A curve of saturation was performed by means of spectroscopic ellipsometry to determine the dose time for the precursors. As a result, the synthesis of ZnO films was obtained using 50 ms for Diethylzinc dosification. To estimate the thickness of Al2O3 layers of the nanolaminates, X-ray photoelectron spectroscopy was used. To characterize the optical response of the samples, room temperature cathodoluminescence spectra were obtained from different multilayer structures. The attenuation of the luminescence was related to the integration of the aluminum oxide on the nanolaminates. As a result, a correlation between the reduction of the luminescence intensity of the multilayer and the increment of the Al2O3 layer thickness was demonstrated. The accurate control on the deposition of thin films makes this process a suitable method to be used in the optoelectronic industry as a precise coating technique with attenuation applications.
关键词： ZnO,Al2O3,ALD,nanolaminates,Optoelectronic attenuator
更新于2025-09-10 09:29:36
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Study on Al <sub/>2</sub> O <sub/>3</sub> /Ge interface formed by ALD directly on epitaxial Ge
摘要： Germanium (Ge) has been attracting considerable attention as a high mobility channel material to enhance the performance of CMOS circuits. One of the most important issues for realization of practical Ge-MOSFET devices with superior performances is requirement to improve qualities of gate dielectric/Ge interfaces. In this work, Al2O3/Ge structures are fabricated by direct atomic layer deposition (ALD) on epitaxialy grown Ge. We indicate that ALD incubation time is fully suppressed by the ALD on a completely clean Ge surface created by Ge epitaxy on a Ge substrate. Moreover, x-ray photoelectron spectroscopy analyses reveal that unintentional formation of a GeO2 at the Al2O3/Ge interface can be almost avoided by the ALD on the epitaxial Ge whereas the interfacial GeO2 layer is present for samples exposed to the air before ALD. These results clearly indicate that direct ALD on epitaxial Ge is a very promising method to signi?cantly improve Ge MOSFET performances.
关键词： Germanium,XPS,Al2O3,ALD,MBE
更新于2025-09-09 09:28:46
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Band alignment of BiOCl/ZnO core shell nanosheets by X-ray photoelectron spectroscopy measurements
摘要： To improve optoelectronic properties of bismuth oxyhalides, hybrid BiOX photocatalytic materials have draw a great attention, because of the separation of photogenerated electron-hole pairs. The band offset and band alignments are considered as the key parameters to elaborate carrier transport properties in heterojunction. In this paper, to determine the band alignment of BiOCl and ZnO heterostructure, BiOCl/ZnO core shell nanosheets with different thickness of shell layer were synthesized. The valence band offset (VBO or DEV) of BiOCl/ZnO heterostructure was determined using X-ray Photoelectron Spectroscopy measurements. The DEV value of 0.294 § 0.10 eV was calculated by using the Zn 2p3/2, Bi 4f5/2 binding energies as references. Taking the band gaps of 3.37 eV and 3.4 eV for ZnO and BiOCl samples into consideration, respectively, we obtained the type-II band alignment of BiOCl/ZnO heterostructure with a conduction band offset (CBO or DEc) of 0.324 § 0.10 eV.
关键词： X-ray photoelectron spectroscopy (XPS),band offset,BiOCl,ZnO,atomic layer deposition (ALD)
更新于2025-09-09 09:28:46
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Improved Gas Sensing Performance of ALD AZO 3-D Coated ZnO Nanorods
摘要： This paper reports an enhancement on the sensing performance of ZnO nanorod ethanol sensors with a new approach by utilizing nested coatings of Aluminum doped ZnO (AZO) thin films by Atomic Layer Deposition (ALD) technology. ZnO nanorods were grown by the hydrothermal method with the ZnO seed layer synthesized on Silicon wafers by ALD. To enhance the sensing performance of ZnO nanorod ethanol sensors, multiple coated AZO thin film 3-D coatings were deposited on the surface of the intrinsic ZnO nanorods by ALD. To investigate the sensing performance of the ZnO nanorods sensor for the detection of ethanol vapor, a gas sensor testing system was designed and built with a sealed reaction chamber and a temperature controller. The demonstrated sensing performance results include the sensing response comparison between ZnO nanorods before and after ALD coatings with AZO films at different temperatures and with various concentrations of input ethanol vapor. The response times and recovery times of ZnO nanorods before and after ALD coatings with AZO thin films were analyzed to investigate the sensing enhancement. The sensing response improvement peaks at 25?C room temperature with approximately 200% enhancement. However, the sensing response improvement decreases as a function of increasing operating temperature.
关键词： ZnO nanorods,gas sensor,ethanol vapor,ALD,AZO
更新于2025-09-09 09:28:46
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Thermal atomic layer deposition of Sn metal using SnCl <sub/>4</sub> and a vapor phase silyl dihydropyrazine reducing agent
摘要： This work explores a novel, thermal atomic layer deposition (ALD) process to deposit tin metal at a low temperature. The authors employ 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (DHP) to reduce SnCl4 on silicon substrates. The authors explored a range of temperatures between 130 and 210 °C to determine the ALD window, which was found to be 170–210 °C. The authors show that this process yields a growth rate of ～0.3 ? per cycle at 190 °C. Furthermore, X-ray photoelectron spectroscopy results showed that the ?lm impurities are reduced for depositions within the ALD window. The reaction mechanism was explored using in situ mass spectrometry and in situ quartz crystal microbalance (QCM). Within the ALD temperature window, the QCM results showed a saturated mass gain during the SnCl4 exposure and a net mass loss during the DHP dose. Consistent with the QCM results, in situ mass spectroscopy data indicate that the DHP exposure step removes surface Cl via formation of volatile trimethylsilyl chloride and pyrazine by-products, effectively reducing the oxidation state of surface-bound Sn. This work is the ?rst thermal Sn metal ALD process to be reported in literature and the oxidation/reduction chemistry presented here may be applied to other metal precursors, increasing the applicability of metal ALD use in industry.
关键词： quartz crystal microbalance,X-ray photoelectron spectroscopy,ALD window,SnCl4,mass spectrometry,tin metal,thermal atomic layer deposition,DHP
更新于2025-09-04 15:30:14
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Interface Properties of GaP/Si Heterojunction Fabricated by PE-ALD
摘要： The properties of n-GaP/p-Si interface as well as their influence on solar cell performance are studied for GaP layers grown by low-temperature (380 °C) plasma-enhanced atomic layer deposition (PE-ALD). The influence of different plasma treatments and RF power values are explored. The increase of RF power leads to a growth transition from amorphous (a-GaP) to microcrystalline GaP (μc-GaP) with either amorphous-GaP/Si or epitaxial-GaP/Si interface, respectively. However, when continuous hydrogen plasma is used the amorphous-GaP/Si interface exhibits better photovoltaic performance compared to the epitaxial one. Values of open circuit voltage, Voc ? 0.45–0.55 V and internal quantum efficiencies, IQE > 0.9 are obtained for amorphous-GaP/Si interfaces compared to Voc ? 0.25–0.35 V and IQE < 0.45 for epitaxial-GaP/Si interfaces. According to admittance spectroscopy and TEM studies the near-surface (30–50 nm) area of the Si substrate is damaged during growth with high RF power of hydrogen plasma. A hole trap at the level of EV t (0.33 ± 0.02) eV is detected by admittance spectroscopy in this damaged Si area. The damage of Si is not observed by TEM when the deposition of the structures with epitaxial-GaP/Si interface is realized by a modified process without hydrogen plasma indicating that the damage of the near-surface area of Si is related to hydrogen plasma interaction.
关键词： admittance spectroscopy,solar cells,PE-ALD,interface,GaP/Si heterojunction
更新于2025-09-04 15:30:14
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Increasing the Electron Mobility of ZnO-Based Transparent Conductive Films Deposited by Open-Air Methods for Enhanced Sensing Performance
摘要： The development of open-air, high-throughput, low-cost thin film fabrication techniques has immense potential and interest in optoelectronics. However, the oxygen-rich atmosphere associated with such processes can have detrimental effects on the electrical properties of the deposited films. An example of this is found in materials based on ZnO, for which atmospheric processing results in low mobility values. This stems mainly from adsorbed oxygen species at the grain boundaries, which limit carrier transport. This paper describes the effect of a low-temperature UV treatment on the electrical properties of ZnO and aluminum doped zinc oxide (ZnO:Al) films deposited by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD). Thanks to the mild UV treatment, a significant decrease in the amount of oxygen traps at the grain boundaries has been observed. This results in a large improvement of the carrier mobility, up to 47 times for undoped ZnO and 16 times for ZnO:Al. The effect of temperature (RT to 220 °C) during the UV treatment on the conductivity of undoped ZnO and ZnO:Al films is discussed. The study of the time-dependent conductivity of ZnO and ZnO:Al films using tunneling emission based models provides a simple means for extracting the grain boundary trap density, a critical parameter in semiconductors that is usually not easy to estimate. We show that the high conductivity of the UV-treated films can be preserved when exposed to oxygen at high temperature thanks to a very thin alumina (Al2O3) barrier layer. Finally, we demonstrate that the effect of UV illumination of thin ZnO films deposited in oxidizing atmospheres can be used to design improved UV or oxygen sensors.
关键词： oxygen trap,electron mobility,spatial ALD,grain boundary,UV treatment
更新于2025-09-04 15:30:14
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Photoelectrochemically Active N‐Adsorbing Ultrathin TiO <sub/>2</sub> Layers for Water‐Splitting Applications Prepared by Pyrolysis of Oleic Acid on Iron Oxide Nanoparticle Surfaces under Nitrogen Environment
摘要： Highly performing photocatalytic surfaces are nowadays highly desirable in energy fields, mainly due to their applicability as photo water-splitting electrodes. One of the current challenges in this field is the production of highly controllable and efficient photoactive surfaces on many substrates. Atomic layer deposition has allowed the deposition of photoactive TiO2 layers over wide range of materials and surfaces. However, nitrogen doping of the growing layers, a highly effective way of controlling the absorption edges of photoactive surfaced, is still a challenging task. Here, the preparation of hierarchical nanostructured surfaces based on Langmuir–Schaefer and atomic layer deposition is proposed. Ultrathin TiO2 layers that are photoelectrochemically active in water splitting are prepared by a relatively low-temperature catalytic decomposition of oleic acid capping layers of iron oxide nanoparticles and the posterior nitrogen adsorption. The results evidence that simple N-adsorption is sufficient to narrow the bandgap of TiO2 layers that is equal to bandgap narrowing (0.12 eV) observed for substitutionally N-doped materials. The photocatalytic activity tests of the prepared surfaces in water-splitting applications demonstrate ≈90% increase in the activity of the N-adsorbing TiO2 layers.
关键词： Langmuir–Schaefer,magnetite (Fe3O4),photocatalysis,titanium dioxide (TiO2),atomic layer deposition (ALD)
更新于2025-09-04 15:30:14
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Removal of Silicone Oil From Intraocular Lens Using Novel Surgical Materials
摘要： To design, fabricate, and evaluate novel materials to remove silicone oil (SiO) droplets from intraocular lenses (IOL) during vitreoretinal surgery.
关键词： IOL,silicone oil,tamponade,PDMS,vitrectomy,lithography,oleophilicity,super hydrophobicity,retinal detachment,ALD
更新于2025-09-04 15:30:14