Deposition Substrate Temperature Research Articles

Novel Spark Method for Deposition of Metal Oxide Thin Films: Deposition of Hexagonal Tungsten Oxide

Hexagonal tungsten trioxide (WO3) layers are grown on indium tin oxide (ITO) substrates using a novel spark deposition system. The effects of deposition time, substrate temperature, and oxygen (O2) flow rate through the chamber on the structural and morphological characteristics as well as the electrochemical response of the layers are examined. It is found that a deposition temperature of 400 °C and O2 flow rate at 60 mL min−1 through the chamber can result in hexagonal WO3 with improved crystallinity and quite effective electrochemical/electrochromic response.

Surface Integrity of TiC Thin Film Produced by RF Magnetron Sputtering

Surface structure determines the performance of materials in service. Enhancing the surface topography of materials with a refractory ceramic coating such as Titanium carbide has gained unprecedented development of recent due to the increase in applications of these functionally graded materials. Radio frequency (RF) magnetron sputtering exhibits a lot of potential in depositing and growing thin film thin. One of the major advantages of RF magnetron sputtering is the ability to be used to coat both the conducting and insulating target. In this research work, RF magnetron sputtering is used to grown titanium carbide (TiC) on Ti6Al4V alloy. The process parameters varied in this study are deposition time, substrate temperature and deposition Power. Other parameters were kept constant throughout the deposition process. Atomic force microscope and Optical profilometer were used to determine the surface roughness of the thin film and scanning electron microscope is employed to analyze the morphology of the surface structure. Homogenous and dense surface morphology was noticed for sample with mid-process parameters and the surface roughness reduces with increase in process parameters.

Substrate heating effects on composition, structure and ferromagnetic resonance properties of CoFeB thin films

Abstract We investigate the ferromagnetic resonance and crystallinity properties of CoFeB thin films grown on Si (1 0 0), at substrate temperatures from 20 °C to 800 °C. The X-ray diffraction data show that the CoFeB films are amorphous when deposited at a substrate deposition temperature of less than 500 °C. X-ray diffraction peak analysis matched the crystalline peaks of films grown at 500 °C to a face-centered cubic (1 1 0) Co7Fe3 phase. Increasing the substrate deposition temperatures increased above 600 °C leads to the formation of a face-centered cubic silicide FeCo2Si (2 2 0) and oxide Fe2CoO4 (4 0 0). Upon crystallization into different phases at a substrate deposition temperature above 500 °C, the soft ferromagnetic properties of CoFeB are lost. The coercivity of the deposited thin films increases from 20 Oe at room temperature to a maximum of 275 Oe at 700 °C. The peak-to-peak ferromagnetic resonance linewidth at 15 GHz, increases from 80 Oe at room temperature to 790 Oe at 500 °C. The grain size of the as-deposited samples increases with substrate temperature from 20-nm at room temperature to 241-nm at 800 °C as determined by atomic force microscopy.

Influence of sputtering parameters on the main characteristics of ultra-thin vanadium nitride films

We researched the relation between deposition and ultra-thin VN films parameters. To conduct the experimental study we varied substrate temperature, Ar and N2 partial pressures and deposition rate. The study allowed us to obtain the films with close to the bulk values transition temperatures and implement such samples in order to fabricate superconducting single-photon detectors.

Insights into the Role of Plasma in Atmospheric Pressure Chemical Vapor Deposition of Titanium Dioxide Thin Films

In this work, the effect of plasma on the chemistry and morphology of coatings deposited by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (AP-PECVD) is investigated. To do so, plasma deposited amorphous titanium dioxide (TiO2) thin films are compared to thin films deposited using Atmospheric Pressure Chemical Vapor Deposition (AP-CVD) not involving the use of plasma. We focus here on the effect and the interest of plasma in the AP-PECVD process over AP-CVD for low substrate temperature deposition. The advantages of AP-PECVD over AP-CVD are often suggested in many articles however no direct evidence of the role of the plasma for TiO2 deposition at atmospheric pressure was reported. Hence, herein, the deposition via both methods is directly compared by depositing coatings with and without plasma using the same CVD reactor. Through the control of the plasma parameters, we are able to form low carbon coatings at low temperature with a deposition rate twice faster than AP-CVD, clearly showing the interest of plasma. Plasma enhanced methods are promising for the deposition of coatings at industrial scale over large surface and at high rate.

Mechanical Properties of Structure-Tunable, Vapor-Deposited TPD Glass

Physical vapor deposition (PVD) with a slow deposition rate and substrate temperature near the glass transition temperature can produce glasses with exceptional properties that include higher density, lower enthalpy, and better kinetic stability than the corresponding properties in ordinary liquid-cooled glass. Despite intensive investigations into thermodynamic and kinetic properties of PVD glasses, little is known about their mechanical properties, such as hardness and creep. In this study, we use nanoindentation to show that the mechanical properties of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) glass can be manipulated by varying the deposition temperature. The elastic modulus of TPD glass was found to be correlated with molecular orientation, whereas the hardness was found to be correlated with density. In addition, our studies reveal that time-dependent deformation plays a key role in the mechanical response of these glasses.

Effect of Deposition Pressure, Nitrogen Content and Substrate Temperature on Optical and Mechanical Behavior of Nanocomposite Al-Si-N Hard Coatings for Solar Thermal Applications

Hard and optically transparent nanocomposite Al-Si-N thin films were deposited using DC magnetron sputtering at different process parameters. There was a significant effect of these parameters on the film properties affecting its mechanical and optical behavior. The nitrogen content or pressure, deposition pressure and substrate temperature strongly influence the phase formation which governs the hardness and optical transparency of the coating. Hardness was measured between 18 and 30 GPa. The band gap could be varied in the range of 3.8-4.2 eV by varying nitrogen pressures in the chamber during deposition. The films showed (0-80)% transparency in UV and visible region depending on the sputtering conditions.

Influence of porosity on the properties of nanostructured tin oxide thin film

Nanostructured tin oxide (SnO2) thin films are deposited using reactive r.f. sputtering by varying deposition time and substrate temperature during deposition. A wide range of tin oxide film thicknesses between 100 nm to 550 nm are deposited by varying the deposition time while substrate temperature during deposition is also varied from room temperature to 400 °C. The homogeneity of the deposited film during deposition is ensured using secondary electron microscopy system (SIMS). The crystal structure and microstructure of the deposited films are investigated using x-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively while the sheet resistance of deposited film is determined by four point probe method. The x-ray diffraction study showed that deposited films are orientated along (110) plane at elevated temperature, manifested with increase of grain size with thickness and substrate temperature except at 300 °C where it decreases. Microstructural studies using cross sectional SEM reveals that 470 nm tin oxide film deposited at room temperature shows highest porosity. The porosity of the films is quantified by using spectroscopic ellipsometry results and it varies from 23.2% to 8.99% for the film deposited at room temperature and 400 °C respectively. LPG response for all deposited films is also measured. The LPG sensitivity for the sensor film of various thicknesses shows linear response with porosity. SnO2 thin films deposited from room temperature to 300 °C shows no significant variation in sensitivity for LPG. The sensor response for LPG decreases sharply for the film deposited above 300 °C. Minimum resistivity 0.3536 Ω.cm is obtained for the tin oxide film deposited at 400 °C. The mechanism of LPG sensing property of nanostructured tin oxide thin film is also explained.

Growth and structures of monolayer and bilayer CeOx nanostructures on Au(111)

The construction of well-defined CeOx/Au(111) model catalysts is key to the understanding of ceria-based catalysts or the Au–CeOx interface in catalytic reactions. Conventionally, owing to the Volmer–Weber growth of ceria on Au(111), ceria nanostructures with controlled layer thickness and well-defined structure have been difficult to grow on Au(111). We explored the influence of growth parameters, such as the substrate temperature for ceria deposition, the flux of Ce atoms and the annealing temperature in this study. We found that ceria prefers to form bilayer nanostructures, i.e. two OCe–O layers, over a large range of growth conditions, whereas monolayer ceria nanostructures could also be obtained on Au(111) with the careful control of growth kinetics. Upon the growth of these well-defined ceria nanostructures, element-specific STM images could also be achieved on their surfaces, which allow the identification of surface and sub-surface O vacancies on ceria. The construction and atomic-scale characterization of these CeOx/Au(111) model catalysts would facilitate the subsequent studies on their surface chemistry and aid our understanding on the catalysis by ceria nanostructures.

Fracture toughness of Mo2BC thin films: Intrinsic toughness versus system toughening

The fracture behaviour and microstructure evolution of sputtered Mo2BC films as a function of their deposition temperature is studied. Bipolar pulsed direct current magnetron sputtering was used to deposit Mo2BC thin films onto Si (100) wafers at substrate temperatures ranging from 380 to 630 °C. Microstructural characterization by transmission electron microscopy revealed that increasing the deposition temperature induces larger and more elongated grains, and a higher degree of crystallinity, transitioning from a partially amorphous to a fully crystalline film. The intrinsic fracture toughness of the Mo2BC films was studied by focussed ion beam milled micro-cantilever bending tests. A mild dependency of the intrinsic fracture toughness on the substrate deposition temperature was found. Fractograph analysis showed that the fracture behaviour was dominated by intergranular fracture or by fracture within the amorphous regions. Additionally, nanoindentation based fracture toughness measurements were used to probe the fracture behaviour of the Mo2BC/Si system, where residual stresses define the ‘apparent’ fracture toughness of the system. Depending on the substrate deposition temperature either compressive or tensile residual stresses developed in the films. This causes a relative change in the system toughness by up to one order of magnitude. The fracture experiments clearly reveal that notched cantilevers provide intrinsic toughness values of a material, while nanoindentation probes the toughness of the entire coating-substrate system. The combination of both techniques provides valuable design information for enhancing fracture resistance of Mo2BC films.

Epitaxial titanium nitride on sapphire: Effects of substrate temperature on microstructure and optical properties

Titanium nitride (TiN) is a mechanically robust, high-temperature stable, metallic material receiving considerable attention for resilient plasmonics. In this work, the authors fabricated six heteroepitaxial TiN films on sapphire using controllably unbalanced reactive magnetron sputtering. They examined the effect of substrate growth temperature on the plasmonic and crystalline quality of the film. Optical properties of all films were obtained from spectroscopic ellipsometry; plasmonic quality factors were determined from the real and imaginary parts of the dielectric function. The authors determined crystallinity using x-ray diffraction and surface morphology using atomic force microscopy. X-ray diffraction showed (111) TiN peaks with Pendellösung fringes indicating consistent heteroepitaxy. Atomic force microscopy showed smooth surfaces with root mean square surface roughness ranging from 0.2 to 2.6 nm. Based on this characterization, the authors determined that the substrate deposition temperature of 550 °C yielded (111)-oriented heteroepitaxial TiN with minimal surface roughness. The authors found that 550 °C also gave highest plasmonic quality factors for all wavelengths, approaching the values of today's best plasmonic materials (such as Au and Ag). Further, the Q-factors at wavelength 1550 nm inversely correlated with calculated lattice constants. Their results indicate that the plasmonic response of TiN is directly linked with structural quality of the film.

Low substrate temperature CdTe solar cells: A review

CdTe photovoltaic technology is one of the first being brought into production together with amorphous silicon (already in the mid 90s Solar Cells Inc. in USA, Antec Solar and BP Solar in Europe were producing 60 × 120cm modules) and it is now the largest in production among thin film solar cells (Photovoltaics Report, 2014).CdTe has high chemical stability and a large variety of successful preparation methods available, which makes this technology one of the most suitable for large area module production.Historically there are two large categories of CdTe photovoltaic devices depending on the substrate deposition temperature, typically low temperature processes are considered when substrate temperature is below 450 °C.In this paper we will describe the last progress of CdTe based thin film solar cells, fabricated with low substrate temperature process, and their pros and cons.

Effect of elevated substrate temperature deposition on the mechanical losses in tantala thin film coatings

Brownian thermal noise in dielectric multilayer coatings limits the sensitivity of current and future interferometric gravitational wave detectors. In this work we explore the possibility of improving the mechanical losses of tantala, often used as the high refractive index material, by depositing it on a substrate held at elevated temperature. Promising results have been previously obtained with this technique when applied to amorphous silicon. We show that depositing tantala on a hot substrate reduced the mechanical losses of the as-deposited coating, but subsequent thermal treatments had a larger impact, as they reduced the losses to levels previously reported in the literature. We also show that the reduction in mechanical loss correlates with increased medium range order in the atomic structure of the coatings using x-ray diffraction and Raman spectroscopy. Finally, a discussion is included on our results, which shows that the elevated temperature deposition of pure tantala coatings does not appear to reduce mechanical loss in a similar way to that reported in the literature for amorphous silicon; and we suggest possible future research directions.

Understanding of post deposition annealing and substrate temperature effects on structural and electrical properties of Gd2O3 MOS capacitor

The purpose of this study is to understand the effects of substrate temperature (ST) and post deposition annealing (PDA) on the structural-electrical properties of Gd2O3 film and to evaluate the electrical performances of the MOS based devices formed with this dielectric. The Gd2O3/Si structures were annealed at 500, 600, 700, and 800 °C under N2 ambient after the films were grown on heated p-Si substrate at various temperatures ranged from 20 to 300 °C by RF magnetron sputtering. For any given ST, the crystallization/grain size increased with increasing PDA temperature. The bump in the accumulation region or continuous decrease in the capacitance values of the inversion region of the C–V curves for 800 °C PDA was not observed. The lowest effective oxide charge density (Qeff) value was obtained to be − 1.13 × 1011 cm−2 from the MOS capacitor with Gd2O3, which is grown on heated Si at 300 °C and annealed at 800 °C. The density of the interface states (Dit) was found to be in the range of 0.84 × 1011 to 1.50 × 1011 eV−1 cm−2. The highest dielectric constant (e) and barrier height $$({\Phi _B})$$ values were found to be 14.46 and 3.68, which are obtained for 20 °C ST and 800 °C PDA. The results show that the negative charge trapping in the oxide layer is generally more than that of the positive, but, it is reverse of this situation at the interface. The leakage current density decreased after 20 °C ST, but no significant change was observed for other ST values.

Metal Templates and Boron Sources Controlling Borophene Structures: An Ab Initio Study

Interlayer binding of 2D borophene phases are determined as a function of hole density (HD) and metal surfaces Cu, Ag, and Au. The Cu surface prefers formation of monolayers whereas the Au surface shows multilayer stacking. Ag surface enables formation of monolayers with higher HD and bilayers for borophenes with lower HD. The growth pattern of bilayers on metal templates are investigated using ab-initio molecular dynamic simulations. Formation of icosahedral B12 clusters and extension to sheets are also studied on Cu surface. Icosahedral sheet formation by boron atom deposition is found to be a thermodynamically unfavorable process on this surface. Thus, structure of borophene phases could also be tuned by modulating the parameters such as boron source or the metal templates, in addition to the substrate temperature and boron atom deposition rate.

Fabrication of Thin Functional Films by Solution Aerosol Thermolysis (SAT)

The technique of air-pressurized solution spray pyrolysis was used to fabricate thin films of La0.75Sr0.25MnO3 (LSM) and CuO-CeO2 on dense YSZ substrates. These films are widely used in several applications such as high temperature ceramic electrochemical cells, membranes and sensors. The technique was tailored to produce films with differing morphologies and thicknesses in terms of applied substrate deposition temperatures. The droplet drying and decomposition kinetics is discussed as a function of substrate temperature, given the other processing parameters (i.e. nozzle to substrate distance, solution flow rate, air pressure/air flow rate and deposition time) constant. A graph-map is drawn containing morphology and quality of fabricated films in terms of substrate temperatures and concentration levels for this particular set of precursor salts in aqueous solutions. Within the deposition temperature range examined, film thicknesses were found to decrease with increasing substrate temperature along with a concomitant change in quality from irregular texture to smoother and of more uniform thickness. A maximum deposition temperature of about 280°C was identified for 0.025M concentration for both types of films which correlates quite well with the Leidenfrost point measured in the literature for solvents with boiling point less than 150°C.

Photo-sensitive Ge nanocrystal based films controlled by substrate deposition temperature

Lowering the temperature of crystallization by deposition of thin films on a heated substrate represents the easiest way to find new means to develop and improve new working devices based on nanocrystals embedded in thin films. The improvements are strongly related with the increasing of operation speed, substantially decreasing the energy consumption and reducing unit fabrication costs of the respective semiconductor devices. This approach avoids major problems, such as those related to diffusion or difficulties in controlling nanocrystallites size, which appear during thermal treatments at high temperatures after deposition. This article reports on a significant progress given by structuring Ge nanocrystals (Ge-NCs) embedded in silicon dioxide (SiO2) thin films by heating the substrate at 400 °C during co-deposition of Ge and SiO2 by magnetron sputtering. As a proof-of-concept, a Si/Ge-NCs:SiO2 photo-sensitive structure was fabricated thereof and characterized. The structure shows superior performance on broad operation bandwidth from visible to near-infrared, as strong rectification properties in dark, significant current rise in the inversion mode when illuminated, high responsivity, high photo-detectivity of 1014 Jones, quick response and significant conversion efficiency with peak value reaching 850% at −1 V and about 1000 nm. This simple preparation approach brings an important contribution to the effort of structuring Ge nanocrystallites in SiO2 thin films at a lower temperature for the purpose of using these materials for devices in optoelectronics, solar cells and electronics on flexible substrates.

Epitaxial Growth of C60 on Rubrene Single Crystals for a Highly Ordered Organic Donor/Acceptor Interface

The highly ordered epitaxial growth of C60 films on rubrene single crystals was demonstrated. The C60 crystals growth commensurate with rubrene (001) surface lattice was confirmed by reflection high energy electron diffraction and X-ray diffraction and grazing incident wide-angle X-ray scattering. Depending on growth conditions, several surface morphologies (rounded, hexagonal, and triangular grains) of C60 grains were observed at the initial growth process. Large grains with layer-by-layer step and terrace structure of C60 were observed at the terrace region of rubrene (001) surface. The growth of high-crystallinity C60 films was achieved at high substrate temperature and slow deposition rate. Long migration length on the substrate which was given by enough substrate temperature enabled the formation of large single crystalline domains.

Preparation of tantalum oxynitride thin film photocatalysts by reactive magnetron sputtering deposition under high substrate temperature

This work spotlights the formation behavior of visible light-responsive tantalum oxynitride (TaON) thin film photocatalysts under high substrate temperature in radiofrequency reactive magnetron sputtering deposition. The results emanating from the optimization of the sputtering conditions demonstrated that sputtered N atoms with high kinetic energy generated by controlling target–substrate distances and total pressures in the sputtering chamber were necessary to grow TaON phase even under N2-rich atmosphere. Based on these findings, TaON thin film photocatalysts were successfully synthesized by single-step sputtering under a high substrate temperature of 1073 K before heat treatment. The optimal thickness of TaON thin film photocatalysts was extrapolated to be 450 nm by photoelectrochemical measurements under visible light irradiation (λ > 450 nm), in which distinct photocurrents corresponding to water oxidation were observed. Moreover, the photoelectrochemical activity was able to be improved by postsynthetic heat treatment in gaseous NH3 and loading with IrO2 nanocolloids as cocatalysts. This finding would be because the thin film photocatalyst after heat treatment in NH3 under appropriate conditions possessed better crystallinity and moderate donor density. The optimized TaON thin film photocatalysts with IrO2 nanocolloids also exhibited photocatalytic activity for H2 evolution from aqueous medium containing methanol as a sacrificial electron donor under visible light irradiation (λ > 450 nm).

Effect of substrate temperature on the characteristics of ZnO films produced by a combination of thermal vapor deposition and oxidation processes

In the present work, ZnO semiconductor films were prepared by following two step processes, namely, thermal vapor deposition of the zinc on the glass substrate followed by oxidative annealing. Substrate temperature during deposition of the zinc was varied. Structural properties and morphology of the ZnO films were investigated by using X-ray diffraction and scanning electron microscopy techniques. Hydrophobic nature of the film was confirmed by using contact angle analyser. Hall measurements facilitated the estimation of the carrier concentration, their mobility and their effect on the conductivity. Photoluminescence spectroscopy was used to analyse the lattice defect concentration in the film. Further, the sensor response of the ZnO film to CO gas was analysed. Sensor fabricated with ZnO films which were prepared by oxidizing Zn films deposited at higher substrate temperature were found to possess better response and faster response-recovery time than the film prepared using lower substrate temperature for zinc deposition.