Deposition Of Oxide Thin Films Research Articles

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

A theoretical study of the atomic layer deposition of HfO2 on Si(1 0 0) surfaces using tetrakis(ethylmethylamino) hafnium and water

The atomic layer deposition (ALD) of hafnium oxide (HfO2) thin film has attracted considerable attention owing to its crucial role in downscaling semiconductor devices. Herein, we theoretically investigated the reaction mechanisms during the ALD of HfO2 thin film (HfO2–ALD) on silicon (Si) surface using tetrakis(ethylmethylamino) hafnium (TEMAH) and water. By using two surface models, fully and partially hydroxylated Si(100) surfaces, we demonstrated that controlling the concentration of hydroxyl groups on the surface is important to enhance the activity for ligand-exchange reactions (LERs) of TEMAH and thereby effectively promote HfO2–ALD. During the precursor pulse, LERs on the fully hydroxylated Si(100) surface easily convert TEMAH into an unsaturated Hf atom with a low energy barrier of 25.8 kJ/mol, while mono(ethylmethylamino) hafnium (MEMAH) is obtained as the final product on the partially hydroxylated Si(100) surface with an energy barrier of 61.3 kJ/mol. The remaining ligand of the adsorbed MEMAH can be removed via LER with water during the water pulse. This work not only provides a better understanding of the conversion of TEMAH into a Hf atom on the hydroxylated Si(100) surface but also offers us more insights into the role of surface hydroxyls in the formation of HfO2 thin films.

Specific method of deposition of aluminium-doped zinc oxide thin films on flexible glass substrates

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DC Sputtering Deposition of Copper Oxide Thin Films Doped with Carbon for Efficient Solar Selective Absorbers

In this work, carbon-doped copper oxide thin films were deposited by the reactive DC sputtering method for use as selective absorbents. The properties of the DC discharge plasma were studied, using the emission spectrum, in the presence of pure argon and by mixing it with oxygen once and carbon dioxide again to know the effect of adding these gases on the properties of the resulting plasma used in the deposition of films. The structural properties of the deposited thin films prepared with different flow ratio of carbon dioxide gas were studied using x-ray diffraction. To examine the selective absorber coatings, the reflectance within the UV-Vis spectrum was measured to calculate the percentage of energy absorbed by solar radiation using numerical integration. The reflectance was also measured in the range from 2.5 to 25 μm to calculate the thermal emission of the solar heater within a temperature of 373 K. Measurements showed good efficiency as a selective absorption layer. The best absorptance of the solar spectrum (α) was 0.8750, and the lowest emittance (ε) in the infrared region was 0.254 at 25% percentage of carbon dioxide in the reactive gas of the sputtering system. So, this ratio has the highest efficiency as a selective absorber.

Stoichiometry and Morphology Analysis of Thermally Deposited V2O5-x Thin Films for Si/V2O5-x Heterojunction Solar Cell Applications.

In recent decades, dopant-free Si-based solar cells with a transition metal oxide layer have gained noticeable research interest as promising candidates for next-generation solar cells with both low manufacturing cost and high power conversion efficiency. Here, we report the effect of the substrate temperature for the deposition of vanadium oxide (V2O5−x, 0 ≤ X ≤ 5) thin films (TFs) for enhanced Si surface passivation. The effectiveness of SiOx formation at the Si/V2O5−x interface for Si surface passivation was investigated by comparing the results of minority carrier lifetime measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. We successfully demonstrated that the deposition temperature of V2O5−x has a decisive effect on the surface passivation performance. The results confirmed that the aspect ratio of the V2O5−x islands that are initially deposited is a crucial factor to facilitate the transport of oxygen atoms originating from the V2O5−x being deposited to the Si surface. In addition, the stoichiometry of V2O5−x TFs can be notably altered by substrate temperature during deposition. As a result, experimentation with the fabricated Si/V2O5−x heterojunction solar cells confirmed that the power conversion efficiency is the highest at a V2O5−x deposition temperature of 75 °C.

Deposition of Iron Oxide Thin Films by Spray Pyrolysis Method

Deposition of Iron Oxide Thin Films by Spray Pyrolysis Method

Adatom-Driven Oxygen Intermixing during the Deposition of Oxide Thin Films by Molecular Beam Epitaxy.

Thin film deposition from the vapor phase is a complex process involving adatom adsorption, movement, and incorporation into the growing film. Here, we present quantitative experimental data that reveals anion intermixing over long length scales during the deposition of epitaxial Fe2O3 and Cr2O3 films and heterostructures by oxygen-plasma-assisted molecular beam epitaxy. We track this diffusion by incorporating well-defined tracer layers containing 18O and/or 57Fe and measure their redistribution on the nanometer scale with atom probe tomography. Molecular dynamics simulations suggest potential intermixing events, which are then examined via nudged elastic band calculations. We reveal that adatoms on the film surface act to "pull up" subsurface O and Fe. Subsequent ring-like rotation mechanisms involving both adatom and subsurface anions then facilitate their mixing. In addition to film deposition, these intermixing mechanisms may be operant during other surface-mediated processes such as heterogeneous catalysis and corrosion.

P‐11: Effects of Ar Dilution on N2O/SiH4 PECVD for the Growth of Silicon Oxide Thin Films with Improved Breakdown Voltage Characteristics

In order to obtain a robust gate dielectric, the nitrogen atom incorporation in the silicon oxide thin film has been investigated in much prior study in recent years. Silicon oxide thin film deposition is mainly performed using SiH4‐N2O plasma by the Plasma enhanced chemical vapor deposition (PECVD) system. Reducing the N2O/SiH4 gas flow ratio increases the nitrogen content in the film. However, the film uniformity dramatically deteriorates as the N2O/SiH4 ratio is decreased and this issue makes the low N2O/SiH4 ratio condition a challenging area for the process condition. In this study, to overcome this problem Argon (Ar) addition was employed to the low N2O/SiH4 ratio plasma and we found that Ar not only allows the thin film to be uniformly deposited by increasing the plasma density due to the penning effect, but also increases Si‐N bond especially under the ratio of 10:1 condition. Even though the silicon oxide thin film was deposited with low N2O/SiH4 gas flow rate, the film uniformity and breakdown voltage characteristics dramatically improved by Ar dilution. In addition, LTPS p‐channel TFT was fabricated by utilizing the improved silicon oxide thin film as a gate dielectric layer and it showed excellent electrical characteristics. This work would be one of the most practical solutions for robust gate dielectric deposition.

Plasma-enhanced atomic layer deposition of aluminum-indium oxide thin films and associated device applications

In this study, aluminum-indium oxide (AIO) semiconductors were fabricated by plasma-enhanced atomic layer deposition (ALD) using trimethyl (dimethylamino)propyl dimethyl indium and trimethylaluminum as the indium and aluminum precursors, respectively. The ALD supercycle consists of n indium oxide subcycles and one aluminum oxide subcycle, where n is 6, 9, 19, or 29. As the number of indium oxide subcycles decrease, the aluminum concentration in the AIO thin film increases and diminishes the thin film crystallinity. In addition, the chemical binding states of the AIO thin film also change with the number of indium oxide subcycles. AIO thin films made with a high number of indium oxide subcycles show stable aluminum oxide bonding and low oxygen related defects. In contrast, AIO thin films deposited with a small number of indium oxide subcycles form unstable AlOx, InOx, and oxygen related defects. The control of aluminum concentration in AIO thin films is essential to control the defect sites in the thin film. Finally, thin film transistors using AIO thin films are fabricated, demonstrating 2.16 V, 6.07 cm2/V s, and 1.50 V/decade with an optimized number of indium oxide subcycles.

Inhibitor-free area-selective atomic layer deposition of SiO2 through chemoselective adsorption of an aminodisilane precursor on oxide versus nitride substrates

Area-selective atomic layer deposition (AS-ALD) offers complementary bottom-up patterning with atomic-level accuracy on pre-defined areas in conjunction with conventional top-down patterning, so it has attracted tremendous interest for enablement of multi-dimensional nanostructures toward sub-10 nm scale technology. In this work, we report a methodology for achieving inherently selective deposition of high-quality oxide thin films through chemoselective adsorption of an aminodisilane precursor, 1,2-bis(diisopropylamino)disilane (BDIPADS), on oxide versus nitride substrates. Density functional theory (DFT) calculations show higher reactivity for adsorption of BDIPADS on OH-terminated SiO2 compared with NH2-terminated SiN surfaces, indicating selective growth of SiO2 films in the SiO2 area. Applying BDIPADS precursor to both SiO2 and SiN substrates results in inherent deposition selectivity of ∼ 1 nm even without the use of inhibitory molecules such as self-assembled monolayers. Using this inherent selectivity as a starting point, we further enhance deposition selectivity using combined ALD-etching supercycle strategies in which HF-wet etching step is periodically inserted after 20 cycles of ALD SiO2, leading to an enlarged deposition selectivity of approximately 5 nm after repeated ALD-etching supercycles. This approach can be envisaged to provide a practically applicable strategy toward highly selective deposition using inherent AS-ALD that can be incorporated into upcoming 3D bottom-up nanofabrication.

Influence of substrate temperature and laser wavelength on the structural, optical and electrical properties of laser ablated tin oxide thin films

The pulsed laser deposition (PLD) of tin oxide thin films on glass substrates has been achieved by ablating tin oxide (SnO2) pellet with Nd-YAG laser. The effects of laser wavelength (532nm, 1064nm) on the deposition as well as substrate temperature (room temperature, 250°C, 450°C) were investigated. The XRD studies were carried out and observed the growth of tetragonal rutile structure of SnO2 films. The FESEM micrographs show changes in surface morphology as a function of laser wavelength as well as the deposition temperature. The optical property investigations using UV-Vis spectra reveal an increase in the band gap with increasing temperature. The investigation of electrical properties using four-point probe method revealed the lower electrical resistivity of the SnO2 films. Thus, the as grown optimized SnO2 conducting thin film electrodes find its potential application in supercapacitor devices.

Distorted zinc coordination polyhedra in bis-(1-eth-oxy-2-{[(2-meth-oxy-eth-yl)imino]-meth-yl}propan-1-olato)zinc, a possible CVD precursor for zinc oxide thin films.

A new metal-organic precursor for the chemical vapor deposition of zinc oxide thin films, [Zn(C9H16NO3)2], has been synthesized and characterized by 1H and 13C NMR spectroscopy, single-crystal X-ray diffraction and thermogravimetric analysis. The asymmetric unit of the title compound consists of two mol-ecules (Z' = 2), with different zinc coordination polyhedra. In one mol-ecule, the metal atom is in a distorted trigonal-bipyramidal ZnN2O3 environment (τ5 = 0.192) with a long bond to an ether O donor atom [Zn-O = 2.727 (6) Å]. In the other, the Zn atom is in a distorted ZnN2O4 octa-hedral environment with long bonds to the ether O donors of both ligands [Zn-O = 2.514 (4) and 2.661 (4) Å; O-Zn-O = 82.46 (14)°]. The crystal structure features weak C-H⋯·O inter-actions.

Influence of the oxygen during the deposition of an indium tin oxide thin film by magnetron sputtering for heterojunction solar cells

Optoelectronic properties of indium and tin oxide thin films depending on the oxygen content in the total gas flow were experimentally investigated during deposition of these films by DC magnetron target sputtering. Relationship of the heterojunction thin-film solar cell output parameters vs. oxygen partial pressure in a vacuum vessel was examined during indium and tin oxide layer deposition. The maximum photovoltaic conversion efficiency of the solar cell was achieved at an oxygen partial pressure in the vacuum vessel of ~6.5 Torr. Keywords: heterojunction thin-film solar element, indium and tin oxide, magnetron sputtering.

Atomic layer deposition of titanium oxide thin films using a titanium precursor with a linked amido-cyclopentadienyl ligand

We studied the atomic layer deposition (ALD) of titanium oxide (TiO2) thin films using a newly developed heteroleptic titanium precursor with a linked ligand.

Plasma Sputtered Tungsten Oxide Thin Film on Poly(lactic acid) for Food Packaging Applications

Biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) are a promising solution to solve the huge environmental and economic issues caused by the enormous consumption of conventional oil-derived polymers, especially in food packaging applications. However, their poor gas barrier properties and high transparency to UV radiation limit their currently commercialization. Therefore, this study is focused on the deposition of tungsten oxide (WOx) thin films on commercial PLA in order to enhance its overall performance. Coatings with different thickness (25, 50 and 100 nm) were deposited by means of radiofrequency (RF) plasma magnetron reactive sputtering. Morphological characterization was carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM). In order to evaluate surface chemical changes due to plasma treatments, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis were performed. The PLA/WOx samples demonstrated remarkable improvements both in UV protection and oxygen barrier properties. In particular, light transmittance was reduced by approximately 95% in the UV-B region, 70% in the UV-A region and 50% in the visible region compared to pristine PLA. Regarding oxygen permeation, a reduction of at least 99.9% was achieved. In addition, the PLA/WOx antibacterial properties against Escherichia coli were also investigated, showing a reduction greater than 5 log10 CFU cm−2 after 24 h for the 50 and 100 nm samples. These results demonstrate the potential of WOx thin coating for sustainable food packaging applications.

A Mechanistic Study of the HF Pulse in the Thermal Atomic Layer Etch of Crystalline and Amorphous HfO2

HfO2 is a high-k material that is crucial in semiconductor devices. Atomic-level control of material processing is required for the fabrication of thin films of this material at nanoscale device sizes. Atomic layer deposition (ALD) and thermal atomic layer etching (ALE) allow the fabrication of ultra-thin films for semiconductor device processing. ALD is a well-known metal oxide thin film deposition technique that enables a high level of control over film thickness. Thermal ALE, which is growing in importance, uses self-limiting halogenation (e.g. HF exposure) producing a non-volatile modified layer. Subsequent ligand exchange reactions remove up to a monolayer of the metal oxide. This modern approach for controlled etching is the reverse of ALD. In gate oxides, the use of amorphous materials is better than crystalline films as the lack of grain boundaries allow for a high breakdown voltage. Amorphous materials have a lower density than crystalline materials.Experimental studies have shown that HfO2 amorphous films have higher etch rates per cycle than crystalline HfO2 films regardless of the fluorination reactant. Given that it is difficult to investigate ALE reactions directly using experimental techniques, first-principles-based atomic-level simulations using density functional theory (DFT) can give deep insights into the precursor chemistry and the reactions that drive the etch of different materials. This contribution presents first-principles density functional theory modelling to examine the etch chemistry of crystalline and amorphous films of HfO2. HF molecules adsorb on the surface of HfO2 by forming hydrogen bonds and may remain intact or dissociate to form Hf-F and O-H bonds. The adsorption of one HF molecule at the bare surface of both the crystalline and amorphous models results in dissociative adsorption at all binding sites. For multiple HF adsorption, we find mixed molecular and dissociative adsorption of HF molecules at the bare surfaces of the crystalline and amorphous models of HfO2. We also present a thermodynamic analysis approach to compare reaction models representing the self-limiting (SL) and continuous spontaneous etch (SE) processes taking place during an ALE pulse.

Advanced processes for low-temperature formation of functional metal oxide based thin films

The analysis the discharge processes in magnetron plasma, target sputtering processes, as well as nucleation and formation of oxide thin films during dc magnetron sputtering is carried out. Particular attention is paid to the phenomenon of instabilities of the current-voltage characteristics of magnetron plasma during the sputtering of oxide targets, the processes of structural transformations of the surface of metal oxide targets under ion bombardment impact, and the mechanisms of low-temperature magnetron deposition of metal oxide thin films. Based on the results of the analysis performed the optimal routes for improving technologies for the low-temperature formation of transparent conductive oxide thin films have been discussed.

Pulsed laser deposition of high-transparency molybdenum oxide thin films

Molybdenum oxide is an intensively studied material, thanks to its high bandgap, high work function, and potentially also photochromism, plasmonic properties, and layered structure. In this contribution, we employ Pulsed Laser Deposition (PLD) from stoichiometric MoO3 and metal Mo target at temperature range of 25 °C–500 °C and oxygen pressure variation of 0.1 mbar–0.4 mbar to deposit high transparency MoO3 layers. The combination of Photothermal Deflection Spectroscopy (PDS) and Spectral Ellipsometry is applied to accurately track all the optical properties. The X-ray diffraction and Scanning Electron Microscopy (SEM) are used to monitor crystallinity and surface morphology. We have observed that with increasing temperature, initially amorphous layer becomes smoother and denser, bandgap narrows and sub-gap absorption increases. This trend can be reversed by increasing oxygen pressure. Above 400 °C, the material starts crystallizing, first in monoclinic β-MoO3 phase and then in orthorhombic α-MoO3 phase. The high pressure promotes crystallinity, however increases surface roughness. Depositions form metal Mo target follow the same trends as in the case of stoichiometric MoO3 target, however the deposition from stoichiometric target produces lower sub-gap absorptance. Sub-gap absorptance centred around 1000 nm depends strongly on deposition temperature and weakly on oxygen pressure.

Comparison of thermal, plasma-enhanced and layer by layer Ar plasma treatment atomic layer deposition of Tin oxide thin films

In this work, Tin oxide (SnOx) thin films have been prepared by different atomic layer deposition (ALD) methods, namely thermal (T-ALD), plasma enhanced (PE-ALD) and subsequent layer by layer Ar plasma treatment (PE-ALD-ALT) modes. In the thermal plasma mode, ozone acts as the oxygen source and Tetrakis(dimethylamino)tin (TDMASn) provides the metal cation. In the plasma-enhanced mode, oxygen plasma was used as the oxygen source. For comparison, we added an Ar plasma treatment step after each layer deposition in the plasma enhanced ALD mode. Compared to T-ALD, the reaction process with O2 plasma as the oxygen source obtained higher growth per cycle (GPC) and crystallinity as well as higher carrier mobility. layer by layer Ar treatment further increased the film carrier concentration and decreased the film resistivity, which also inevitably caused a further increase in the roughness and residual stress in the film.

Influence of thickness and deposition angle on structural and optical properties of manganese oxide thin films

Manganese oxide thin films were produced on glass substrates by resistive evaporation at room temperature. The layers with different thickness (30 and 90 nm) at different deposition angles (0 and 40°) were prepared by electron gun evaporation method under ultra-high vacuum condition. After deposition of pure manganese oxide thin films a post-annealing process was used in a uniform oxygen flow of 300 (sccm) and at 500 K annealing temperature. Optical transmittance and reflectance of the layers were measured in the wavelength of 350–850 nm by a spectrophotometer. Kramers–Kronig relations were used to calculate the optical constants. The influence of oxygen flow and annealing temperature on optical properties is investigated. It was found that film thickness and deposition angle plays a significant role on the nanostructures as well as optical properties of layers and cause major variations in behavior of thin manganese oxide films. The physical properties of materials were characterized by X-ray diffraction (XRD), FE-SEM, AFM, EDAX, and UV-VIS techniques.