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Photocatalytic properties of TiO2@Polymer and TiO2@Carbon aerogel composites prepared by atomic layer deposition
摘要： Monolithic structured TiO2/aerogel composites were prepared from resorcinol-formaldehyde polymer aerogel (RFA) and its carbon aerogel (RFCA) derivative. A resorcinol-formaldehyde hydrogel was synthesized in a sol-gel reaction and transformed into polymer aerogel by supercritical drying. The RFA was converted to carbon aerogel by pyrolysis at 900 °C in dry N2. Amorphous and crystalline TiO2 layers were grown from TiCl4 and H2O precursors by atomic layer deposition (ALD) at 80 °C and 250 °C, respectively, on both RFA and RFCA. The substrates and the composites were studied by N2 adsorption, TG/DTA-MS, Raman, SEM-EDX and TEM techniques. Their photocatalytic activity was compared in the UV catalyzed decomposition reaction of methyl orange dye.
关键词： ALD,photocatalysis,carbon aerogel,TiO2,resorcinol-formaldehyde polymer aerogel
更新于2025-11-20 15:33:11
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Effect of HCl Cleaning on InSb-Al<sub>2</sub>O<sub>3</sub> MOS Capacitors
摘要： In this work, the role of HCl treatments on InSb surfaces and InSb-Al2O3 dielectric interfaces is characterised. X-ray photoelectron spectroscopy (XPS) measurements indicate that HCl diluted in and rinsed with isopropanol (IPA) results in a surface layer of InCl3 which is not present for similar HCl-water processes. Furthermore, this InCl3 layer desorbs from the surface between 200°C and 250°C. Metal-oxide-semiconductor capacitors (MOSCAPs) were fabricated using atomic layer deposition (ALD) of Al2O3 at 200°C and 250°C and the presence of InCl3 was associated with a +0.79 V flatband voltage shift. The desorption of the InCl3 layer at 250°C reversed this shift but the increased process temperature resulted in increased interface-trapped charge (Dit) and hysteresis voltage (VH). This shift in flatband voltage, which does not affect other figures of merit, offers a promising route to manipulate the threshold voltage of MOS transistors, allowing enhancement-mode and depletion-mode devices to be fabricated in parallel.
关键词： surface cleaning,III-V,ALD,Al2O3,InSb,dielectric interface,MOSCAP,HCl
更新于2025-11-14 17:28:48
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Biocompatible organic–inorganic hybrid materials based on nucleobases and titanium developed by molecular layer deposition
摘要： We have constructed thin films of organic–inorganic hybrid character by combining titanium tetra-isopropoxide (TTIP) and the nucleobases thymine, uracil or adenine using the molecular layer deposition (MLD) approach. Such materials have potential as bio-active coatings, and the bioactivity of these films is described in our recent work [Momtazi, L.; Dartt, D. A.; Nilsen, O.; Eidet, J. R. J. Biomed. Mater. Res., Part A 2018, 106, 3090–3098. doi:10.1002/jbm.a.36499]. The growth was followed by in situ quartz crystal microbalance (QCM) measurements and all systems exhibited atomic layer deposition (ALD) type of growth. The adenine system has an ALD temperature window between 250 and 300 °C, while an overall reduction in growth rate with increasing temperature was observed for the uracil and thymine systems. The bonding modes of the films have been further characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction, confirming the hybrid nature of the as-deposited films with an amorphous structure where partial inclusion of the TTIP molecule occurs during growth. The films are highly hydrophilic, while the nucleobases do leach in water providing an amorphous structure mainly of TiO2 with reduced density and index of refraction.
关键词： bioactive materials,ALD,MLD,hybrid materials,nucleobases
更新于2025-11-14 15:14:40
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Structural study of MgO and Mg-doped ZnO thin films grown by atomic layer deposition
摘要： Pure MgO, 1 and 10 at% Mg-doped ZnO layers were grown by atomic layer deposition technique onto (001)-oriented α-Al2O3 and GaN substrates. The structure and the microstructure of the deposited layers were studied by TEM in detail. The pure MgO layer starts to grow with epitaxy with (100)-type defects that transforms to random orientation. In the 10 at% Mg-doped samples epitaxial cubic MgO buffer layer forms at the interface. This buffer layer helps the ZnO to grow epitaxially in the case of α-Al2O3 substrate forming a ZnO/MgO/c-plane α-Al2O3 hetero-structure showing higher mobility with lower carrier concentration, while in the case on GaN substrate the ZnO is strongly textured. Consequently for higher concentration Mg doping (with the formation of MgO buffer layer) α-Al2O3 is better choice to grow epitaxial ZnO layer. The 1 at% Mg-doping of the epitaxial ZnO layer grown onto GaN substrate was successfully implemented, while in the case of α-Al2O3 substrate a thin cubic MgO buffer layer forms. This shows that the success of low concentration Mg doping in ZnO largely depends on the choice of substrate material as well.
关键词： Mg-doped ZnO,ALD,MgO,TEM
更新于2025-09-23 15:23:52
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Barrier height modification in Au/Ti/n-GaAs devices with a $$\hbox {HfO}_{2}$$HfO2 interfacial layer formed by atomic layer deposition
摘要： X-ray photoelectron spectroscopy has been carried out to characterize the surface of the hafnia (HfO2) thin films grown on n-GaAs wafer by atomic layer deposition, and the surface morphology of the HfO2 layer on GaAs has been analysed using atomic force microscopy. The barrier height (BH) values of 1.03 and 0.93 eV (300 K) for the Au/Ti/HfO2/n-GaAs structures with 3- and 5-nm HfO2 interfacial layers, respectively, have been obtained from the I–V characteristics of the devices, which are higher than the value of 0.77 eV (300 K) for the Au/Ti/n-GaAs diode fabricated by us. Therefore, it can be said that the HfO2 thin layer at the metal/GaAs interface can also be used for BH modification as a gate insulator in GaAs metal-oxide semiconductor (MOS) capacitors and MOS field-effect transistors. The ideality factor values have been calculated as 1.028 and 2.72 eV at 400 and 60 K; and as 1.04 and 2.58 eV at 400 and 60 K for the metal–insulating layer–semiconductor (MIS) devices with 3- and 5-nm interfacial layers, respectively. The bias-dependent BH values have been calculated for the devices by both Norde’s method and Gaussian distribution (GD) of BHs at each sample temperature. At 320 K, the (cid:2)b(V ) value at 0.70 V for a 3-nm MIS diode is about 1.08 eV from the (cid:2)b(V ) vs. V curve determined by the GD, and about 0.99 eV at 0.58 V for a 5-nm MIS diode. It has been seen that these bias-dependent BH values are in close agreement with those obtained by Norde’s method for the same bias voltage values.
关键词： metal–insulating layer–semiconductor (MIS) device,Barrier height modification and inhomogeneous,bias-dependent barrier height,temperature-dependent MIS diode parameters,atomic layer deposition (ALD)
更新于2025-09-23 15:23:52
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22.3: Low cost fabrication of high contrast ratio and high transmission wire grid polarizer by nanoimprint lithography
摘要： This paper proposes a novel approach for low cost fabrication of large area wire grid polarizer (WGP). WGPs regarded as one potential alternative to traditional rear polarizer and DBEF possess the advantages of large contrast ratio (CR), high transmission. To date WGPs can be fabricated through electron beam direct write, which is slow and expensive, therefore not suitable for large area application. With the development of nano-fabrication methods, for instance, nanoimprint lithography (NIL), large area WGP can be made at low cost and fast speed. Furthermore, flexible polarizer can also be made through roll-to-roll (R2R) NIL. In this paper, a WGP with high TM transmission of around 85% and low TE transmission down to 0.2% through the visible light spectra will be realized through nanofabrication. The contrast ratio of the WGP can reach >450 with peak value >3000. For the fabrication process, atom layer deposition (ALD) will be utilized to prepare imprint mask which can achieve highly precise control of expected structure. In this paper, characterization of the designed WGP will also be narrated in the back part, including transmission, CR and the SEM schematic diagram. We believe that low cost fabrication method shows the potential to be adopted for industrial fabrication of polarizer in the future.
关键词： atom layer deposition (ALD),large area fabrication,low cost fabrication,wire grid polarizer (WGP),high contrast ratio,nanoimprint lithography (NIL),high TM transmission
更新于2025-09-23 15:22:29
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Design and Characterisation of Titanium Nitride Subarrays of Kinetic Inductance Detectors for Passive Terahertz Imaging
摘要： We report on the investigation of titanium nitride (TiN) thin films deposited via atomic layer deposition (ALD) for microwave kinetic inductance detectors (MKID). Using our in-house ALD process, we have grown a sequence of TiN thin films (thickness 15, 30, 60 nm). The films have been characterised in terms of superconducting transition temperature Tc, sheet resistance Rs and microstructure. We have fabricated test resonator structures and characterised them at a temperature of 300 mK. At 350 GHz, we report an optical noise equivalent power NEPopt ≈ 2.3 × 10?15 W/√Hz, which is promising for passive terahertz imaging applications.
关键词： Titanium nitride,ALD,Kinetic inductance detector
更新于2025-09-23 15:22:29
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Particle atomic layer deposition
摘要： The functionalization of fine primary particles by atomic layer deposition (particle ALD) provides for nearly perfect nanothick films to be deposited conformally on both external and internal particle surfaces, including nanoparticle surfaces. Film thickness is easily controlled from several angstroms to nanometers by the number of self-limiting surface reactions that are carried out sequentially. Films can be continuous or semi-continuous. This review starts with a short early history of particle ALD. The discussion includes agitated reactor processing, both atomic and molecular layer deposition (MLD), coating of both inorganic and polymer particles, nanoparticles, and nanotubes. A number of applications are presented, and a path forward, including likely near-term commercial products, is given.
关键词： Coating,Particle ALD,Nanoparticle,Nanolayers,Atomic layer deposition
更新于2025-09-23 15:22:29
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Decoupling Effects of Surface Recombination and Barrier Height on p-Si(111) Photovoltage in Semiconductor|Liquid Junctions via Molecular Dipoles and Metal Oxides
摘要： This work provides insight into carrier dynamics in a model photoelectrochemical system comprised of a semiconductor, metal oxide, and metal. To isolate carrier dynamics from catalysis, a common catalytic metal (Pt) is used in concert with an outer-sphere redox couple. Silicon (111) substrates were surface-functionalized with electronegative aryl moieties (p-nitrophenyl and m-dinitrophenyl). A mixed monolayer using p-nitrophenyl/methyl exhibited high surface quality as determined by X-ray photoelectron spectroscopy (low surface SiOx content) and low surface recombination velocity. This substrate also exhibited the expected positive surface dipole, as evidenced by rectifying J?V behavior on p-type substrates, and by positive photovoltage measured by surface photovoltage spectroscopy. Its close molecular relative m-dinitrophenyl exhibited poor electronic surface quality as indicated by high SiOx coverage and high surface recombination velocities (S > 3000 cm s?1). Photoelectrochemical J?V measurements of p-type Si-functionalized surfaces in contact with a high concentration (50 mM) of methyl viologen (MV2+) in aqueous media revealed VOC values that are correlated with the measured barrier heights. In contrast, low-concentration (1.5 mM) MV2+ experiments revealed significant contributions from surface recombination. Next, the electronic and (photo)electrochemical properties were studied as a function of ALD metal oxide deposition (TiO2, Al2O3) and Pt deposition. For the m-dinitrophenyl substrate, ALD deposition of both TiO2 and Al2O3 (150 °C, amorphous) decreased the surface recombination velocity. Surprisingly, this TiO2 deposition resulted in negative shifts in VOC for all surfaces (possibly ALD-TiO2 defect band effects). However, Pt deposition recovered the efficiencies beyond those lost in TiO2 deposition, affording the most positive VOC values for each substrate. Overall, this work demonstrates that (1) when carrier collection is kinetically fast, p-Si(111)?R devices are limited by thermal emission of carriers over the barrier, rather than by surface recombination. And (2) although TiO2 |Pt improves the PEC performance of all substrates, the beneficial effects of the underlying (positive) surface dipole are still realized. Lastly (3) Pt deposition is demonstrated to provide beneficial charge separation effects beyond enhancing catalytic rates.
关键词： solar fuels,interfacial dipole,atomic layer deposition (ALD),surface functionalization,band-edge modulation,photoelectrochemistry
更新于2025-09-23 15:22:29
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Characteristics of Al<sub>2</sub>O<sub>3</sub>/native oxide/n-GaN capacitors by post-metallization annealing
摘要： This work investigated characteristics of Al2O3/native oxide/n-GaN MOS capacitors by post-metallization annealing (PMA). A native oxide interlayer which composed of ε- and γ-Ga2O3 phases (Native oxide) and the reduced amount of one (Reduced) on n-GaN were prepared by cleaning only a sulfuric acid peroxide mixture (SPM) and both SPM and buffered hydrofluoric acid, respectively. The effect of trimethylaluminum precursor on removal of a native oxide layer was not observed during Al2O3 deposition using atomic layer deposition. An as-grown capacitor (Native oxide) exhibited a small flatband voltage (Vfb) hysteresis of ~30 mV and a large frequency dispersion, suggesting that the initial growth of the Al2O3 resulted in the formation of electrical defects on the GaN surface. Both the Vfb hysteresis and frequency dispersion were drastically improved by PMA of the device at 300°C. The positive fixed charge values (QIL) estimated from the relationships between capacitance equivalent thickness and Vfb were +6.1 × 10^12 and +0.4 - 1.0 × 10^12 cm^-2 for as-grown and PMA-processed capacitors in the PMA temperature range of 300 - 600°C, respectively. The interface state density (Dit) determined using a conductance method was also significantly reduced (by an order of magnitude) after PMA processing at 300°C. These trends in the QIL and Dit data were observed in both the Native oxide and Reduced capacitors, indicating that this interlayer does not greatly affect fixed charge generation at the Al2O3/native oxide and Al2O3/modefied native oxide interfaces. As a result, two types of treatments result in insignificant difference in the electrical properties of the capacitors.
关键词： flatband voltage,GaN,Al2O3 dielectric,ALD,fixed charge,native oxide interlayer
更新于2025-09-23 15:22:29