One of many challenges for niobium (Nb) based superconducting devices is the improvement over the surface morphology and superconducting properties as well as the reduction of defects. We employed a novel deposition technique, i.e. biased target ion beam deposition technique (BTIBD) to prepare Nb thin films with controlled crystallinity and surface morphology. We found that the target current (ITarget) and the target bias (VTarget) were critical to the crystallinity and surface morphology of Nb films. The high target current (ITarget >500 mA and VTarget = 400 V bias) during the deposition degraded the Nb crystallinity, and subsequently reduced the critical temperature for superconductivity (Tc). VTarget was critical to the surface morphology, i.e. grain size and shape and the surface roughness. The optimized growth condition yielded very smooth film with RMS roughness of 0.4 nm that was an order of magnitude smoother than that of Nb films by sputtering process. The critical temperature for superconductivity was also close to the value of the bulk Nb. The quality of Nb film was evident in the presence of a very thin proximity layer (~ 0.8 nm). The experimental results demonstrated that the preparation of smooth Nb films with adequate superconductivity by BTIBD could serve as a base electrode for the in-situ magnetic layer or insulating layer for superconducting electronic devices.
Magnetic tunnel junctions (MTJ) with AlOx barrier were fabricated by a deposition tool called Biased Target Ion Beam Deposition (BTIBD) using low energy ion source (0-50 eV) and voltage biased targets. The BTIBD system applies bias voltage directly and only on the desired targets, providing enough sputtering energy and avoiding "overspill" contamination during film deposition. The successful deposition of AlOx-MTJs demonstrated the capability of BTIBD to make multilayer structures with good film quality. MTJ thin film surface roughness and intermixing between layers are among the key problems …
Crystallization is a key for ferroelectricity which is a collective behavior of microscopic electric dipoles. On the other hand, uncontrolled crystallization leads to uneven morphology and random crystal orientations, which undermines the application potential of ferroelectric thin films. In this work, we introduce a film fabrication method of low-temperature physical vapor deposition followed by restrained crystallization, with electrical properties monitored in real-time by in situ measurements. This method was adopted to fabricate films of 2-methylbenzimidazole (MBI), whose molecule crystal…
Aluminum oxide thin films were deposited on silicon substrates under different deposition conditions using pulse pressure metal organic chemical vapour deposition (PP-MOCVD). The current study investigates into the growth mechanism of the deposited film and the control of the film morphology by varying the processing parameters of PP-MOCVD - choice of solvent, concentration, and presence of a shield. Aluminum sec-butoxide (ASB) was used as the aluminum source while hexane and toluene were used as the solvents. The films were deposited at 475oC at different precursor concentrations. It was obse…
In this paper, we report the growth of NaxCoO2 thin films by pulsed-laser deposition (PLD). It is shown that the concentration of sodium is very sensitive to the substrate temperature and the target-substrate distance due to the evaporation of sodium during the deposition. alpha prime-phase Na0.75CoO2 and gamma- phase Na0.71CoO2 thin films can be obtained with different conditions. Correspondingly, the surface morphology of the films changes from flake-like to particle-like. The temperature dependence of resistivity for the films prepared with the optimal condition shows metallic behavior, con…
We have studied surface morphology and magnetic properties of Fe/MgO(001) films deposited at an angle varying between 0o and 60o with respect to the surface normal and with azimuth along the Fe[010] or the Fe[110] direction. Due to shadowing, elongated grains appear on the film surface for deposition at sufficiently large angle. X-ray reflectivity reveals that, depending on the azimuthal direction, films become either rougher or smoother for oblique deposition. For deposition along Fe[010] the pronounced uniaxial magnetic anisotropy (UMA) results in the occurrence of reversed two-step and of t…
Cu2Ta4O12 (CTaO) thin films were successfully deposited on Si(100) substrates by pulsed-laser deposition technique. The crystalline structure and the surface morphology of the CTaO thin films were strongly affected by substrate temperature, oxygen pressure and target - substrate distance. In general during deposition of CTaO the formation of a Ta2O5 phase appeared, on which CTaO grew with different orientations. We report on the experimental set-up, details for film deposition and the film properties determined by SEM, EDX and XRD.
In this paper we report the deposition of epitaxial thin films of Nd1-xSrxCoO3 with x=0, 0.2 and 0.5 on single crystalline substrates (SrTiO3 and LaAlO3) carried out by means of rf-magnetron sputtering. The deposited films are all completely oriented and epitaxial and characterized by a nanocrystalline morphology. As-deposited films have an average roughness around 1 nm while after the thermal treatment this increases up to 20 nm while preserving the nanocrystalline morphology. All the films deposited on SrTiO3 have shown to be under a certain degree of tensile strain while those on the LaAlO3…
Pulsed laser deposition from a Nd:YAG laser was employed in production of hundreds of nanometer thick quasicrystalline Ti-Zr-Ni films on glass substrate. The influence of deposition temperature Ts on the structure, morphology and microstructure of the films across their thickness was investigated. The morphology and microstructure features were evaluated by X-ray diffraction and transmission electron microscopy techniques. The low deposition temperatures were found to produce films with nanometer sized grains embedded in an amorphous matrix. The grains exhibit quasicrystalline order. The highe…
Rhombohedral B4C coatings were synthesised on fused silica substrates by CO2 laser-assisted chemical vapour deposition (LCVD), using a dynamic reactive atmosphere of BCl3, C2H4 and H2. Films with carbon content from 15 to 22 at.% were grown at deposition rates as high as 0.12 micrometers per second. The kinetics of the reactive system used to deposit the B4C films and the influence of growth conditions on the structure and morphology of the deposits were investigated. Keywords: Rhombohedral boron carbide (r-B4C), Laser-CVD, growth kinetics.
Thin films of gold were deposited on single crystalline CaF2 substrates of (100) and (111) orientation by thermal evaporation. The resulting film structure was analyzed by means of atomic force microscopy in dependence of substrate temperature and deposition thickness. A marked substrate dependency was found. On CaF2 (100), extended and flat plateaus with diameters of several hundreds of nanometers form in a network-like arrangement for deposition thicknesses between 30 and 45 nm. On CaF2 (111), closed films of small average roughness develop at film thicknesses between 70 and 90 nm. These fil…
We demonstrated that chemical vapor deposition of graphene on Cu films strongly enhances their thermal diffusivity and thermal conductivity. Deposition of graphene increases the thermal conductivity of 9 micrometer (25 micrometer) thick Cu films by up to 24% (16%) near room temperature. Interestingly, the observed improvement of thermal properties of graphene coated Cu films is primarily due to changes in Cu morphology during graphene deposition and associated with it temperature treatment rather than graphene's action as an additional heat conducting channel. Enhancement of thermal properties…
Pulsed Laser Deposition (PLD) of homoepitaxial SrTiO3 <001> was studied with in-situ x-ray specular reflectivity and surface diffuse x-ray scattering. Unlike prior reflectivity-based studies, these measurements access both the time- and the length-scales of the evolution of the surface morphology during growth. In particular, we show that this technique allows direct measurements of the diffusivity for both inter- and intra-layer transport. Our results explicitly limit the possible role of island break-up, demonstrate the key roles played by nucleation and coarsening in PLD, and place an upper…
Carbon is one of the most investigated materials and shows chaotic behavior in terms of evolving structure. Synthesizing carbon materials largely depend on the deposition technique, process parameters, condition of substrate surface and ratios of the gaseous chemistry. A variety of techniques have been employed to depositing carbon films from various gaseous mixtures to different substrate materials. In this study, carbon thin and thick films are discussed for different techniques known as hot filament chemical vapor deposition and microwave plasma chemical vapor deposition where their synthes…
Here we report mid infrared (mid-IR) photothermal response of multi layer MoS2 thin film grown on crystalline (p-type silicon and c-axis oriented single crystal sapphire) and amorphous substrates (Si/SiO2 and Si/SiN) by pulsed laser deposition (PLD) technique. The photothermal response of the MoS2 films was measured as changes in the resistance of MoS2 films when irradiated with mid IR (7 to 8.2 μm) source. We show that it is possible to enhance the temperature coefficient of resistance (TCR) of the MoS2 thin film by controlling the interface through proper choice of substrate and growth condi…
Control of Cu morphology on TaN barrier and combined Ru-TaN barrier/liner substrates for nanoscale interconnects from atomistic kinetic Monte Carlo simulations
本研究利用基于 DFT 能垒的原子尺度 kMC 模拟，考察不同 Ru 掺入量、温度和分压下 TaN 及 Ru-TaN 复合阻挡层/衬垫层上的 Cu 沉积形貌，以优化纳米互连体积。
Nanographitic structures (NGSs) with multitude of morphological features are grown on SiO2/Si substrates by electron cyclotron resonance - plasma enhanced chemical vapor deposition (ECR-PECVD). CH4 is used as source gas with Ar and H2 as dilutants. Field emission scanning electron microscopy, high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy are used to study the structural and morphological features of the grown films. Herein, we demonstrate, how the morphology can be tuned from planar to vertical structure using single control parameter namely, dilution of CH4 w…
Oblique angle deposited oxide thin films have opened up new dimensions in fabricating optical interference devices with tailored refractive index profile along thickness by tuning its microstructure by varying angle of deposition. Microstructure of thin films strongly affects surface morphology as well as optical properties. Since surface morphology plays an important role for the qualification of thin film devices for optical or other applications, it is important to investigate morphological properties. In present work, HfO2 thin films have been deposited at several oblique angles. Morpholog…
Using two different experimental techniques, namely, chemical vapor deposition (CVD) and physical vapor deposition (PVD), we deposited a Lead sulphide (PbS) thin films with a very small lifetime. We investigated the morphology of the obtained PbS films using various techniques i.e.AFM, SEM, EDAX, AES and HRTEM . In the case of CVD, we found that the surface consists of grains with dimensions in the plane (diameter to 300 nm and height up to 200 nm), while the same order of the grain size has been observed for PVD. On the other hand, SEM investigation reveals that the PbS particles with various…
We present a molecular dynamics simulation scheme that we apply to study the time evolution of the self-organized growth process of metal cluster assemblies formed by sputter-deposited gold atoms on a planar surface. The simulation model incorporates the characteristics of the plasma-assisted deposition process and allows for an investigation over a wide range of deposition parameters. It is used to obtain data for the cluster properties which can directly be compared to recently published experimental data for gold on polystyrene (M. Schwartzkopf \textit{et al}., ACS Appl. Mater. Interfaces \…
Nanocomposite NiO:Au thin films, formed by gold nanoparticles embedded in a nickel oxide matrix, have been grown by reactive pulsed laser deposition (R-PLD). Two actively synchronized nanosecond laser sources, a KrF excimer laser (248 nm) and a Nd:YAG laser (355 nm), were used for the simultaneous ablation of nickel and gold targets in oxygen ambient. The morphology, composition, and optical properties of the obtained nanocomposites were investigated and were found to correlate with the concentration of Au nanoparticles. Further, the NiO:Au nanocomposites have been tested as hydrogen sensors. …
The electron field emission of patterned films of nitrogenated carbon nanotubes is shown to be decisively influenced by the deposition conditions. The growth was carried out by decomposing methane in a nitrogen/ammonia atmosphere using hot filament chemical vapor deposition (CVD). The diameter of the produced tubes depended critically on the distance between substrate and filament, and the field emission properties applied fields needed for electron emission, field amplification factor) could be directly correlated to the film morphology. This demonstrates the possibility of tuning the field e…
In this work, the authors fabricated Cu2O porous nanostructured films (PNFs) on glass slide substrates by the newly developed positive bias deposition approach in a balanced magnetron sputtering (MS) system. It was found that the surface morphology, crystal structure and optical property of the as-deposited products were greatly dependent on the applied positive substrate bias. In particular, when the substrate was biased at +50 V and +150 V, both of the as-prepared Cu2O PNFs exhibited a unique triangular pyramids-like structure with obvious edges and corners and little gluing, a preferred ori…
In this work, we report on the addition of GeH4 gas during homoepitaxial growth of 4H-SiC by chemical vapour deposition. Ge introduction does not affect dramatically the surface morphology and defect density though it is accompanied with Ge droplets accumulation at the surface. The Ge incorporation level inside the 4H-SiC matrix, ranging from few 1017 to few 1018 at.cm-3, was found to be mainly affected by the growth temperature and GeH4 flux. Other growth parameters like C/Si ratio, polarity, or off-orientation did not show any significant influence. On the other hand, adding GeH4 led to the …
Issues of morphology, nucleation and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (<600 deg C) and high (>600 deg. C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibilit…
Supported carbon nanosheets and carbon nanotubes served as sacrificial templates for preparing spacious TiO2 photocatalytic thin films. Amorphous TiO2 was deposited conformally on the carbonaceous template material by atomic layer deposition (ALD). Upon calcination at 550°C, the carbon template was oxidatively removed and the as-deposited continuous amorphous TiO2 layers transformed into interlinked anatase nanoparticles with an overall morphology commensurate to the original template structure. The effect of type of template, number of ALD cycles and gas residence time of pollutant on the pho…
Magnetic anisotropy is a key parameter of magnetic materials as it decides the response in the presence of an external magnetic field. The artificial tailoring of magnetic anisotropy by manipulating surface and interface morphology is attracting widespread interest for its application in spintronic and magnetic memory devices. In this perspective, the primary focus of this thesis has been inducing and tailoring magnetic anisotropy in thin film-based systems via the engineering of structure and surface/interfacial morphology. For this purpose, instead of multistep, expensive lithographic techni…
A sputter deposition source for use in ultrahigh vacuum (UHV) is described and some properties of the source are analyzed. The operating principle is based on the design developed by Mayr et al. [Rev. Sci. Instrum. 84, 094103 (2013)], where electrons emitted from a filament ionize argon gas, and the Ar$^+$ ions are accelerated to the target. In contrast to the original design, two grids are used to direct a large fraction of the Ar$^+$ ions to the target, and the source has a housing cooled by liquid nitrogen to reduce contaminations. The source has been used for deposition of zirconium, a mat…
The statistical effects of different conditions in physical vapor deposition, such as sputter deposition, have on thin film morphology has long been the subject of interest. One notable effect is that of column development due to differential chamber pressure in the well-known empirical model called Thornton's Structure Zone Model. The model is qualitative in nature and theoretical understanding with quantitative predictions of the morphology is still lacking due to, in part, the absence of a quantitative description of the incident flux distribution on the growth front. In this work, we propo…
Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower w…
Morphology of metal thin layers deposited on polished surfaces of LiNbO$_3$ crystal with dissimilar electric charges has been studied using various methods of vacuum evaporation. The principal goal of the work is to optimizemethods of thin metal coating deposition applied to polar surfaces of LiNbO$_3$ crystal. The conducted research has demonstrated that Cr deposition on LiNbO$_3$ crystal faces is characterized by dissimilar polarity results in growth difference conditions of Cr films. The principal role here is played by the sign of the electric charge on the crystal surface along with the t…
(111)NiO epitaxial layers are grown on c-sapphire substrates by pulsed laser deposition (PLD) technique. Structural and morphological properties of the films are studied using in-plane as well as out-of-plane high resolution X-ray diffraction and atomic force microscopy techniques as functions of growth temperature, oxygen pressure and the pulses count of the laser. The study shows that continuous epitaxial films of thickness as low as 3 nm with high crystalline quality, smooth surface and interface morphology can be grown by this technique. The study also reveals the co-existence of 60°-rotat…
We have investigated morphology of the lateral surfaces of PbTe crystal samples grown from melt by the Bridgman method sputtered by Ar+ plasma with ion energy of 50-550 eV for 5-50 minutes under Secondary Neutral Mass Spectrometry (SNMS) conditions. The sputtered PbTe crystal surface was found to be simultaneously both the source of sputtered material and the efficient substrate for re-deposition of the sputtered material during the depth profiling. During sputtering PbTe crystal surface is forming the dimple relief. To be redeposited the sputtered Pb and Te form arrays of the microscopic surf…
Layered van der Waals (vdW) materials grown by physical vapor deposition techniques are generally assumed to have a weak interaction with the substrate during growth. This leads to films with relatively small domains that are usually triangular and a terraced morphology. In this paper, we demonstrate that Bi2Se3, a prototypical vdW material, will form a nano-column morphology when grown on GaAs(001) substrates. This morphology is explained by a relatively strong film/substrate interaction, long adatom diffusion lengths, and a high reactive selenium flux. This discovery paves the way toward gro…
Porous metal oxides with nano-sized features attracted intensive interest in recent decades due to their high surface area which is essential for many applications, e.g. Li ion batteries, photocatalysts, fuel cells and dye-sensitized solar cells. Various approaches were so far investigated to synthesize porous nanostructured metal oxides, including self-assembly and template-assisted synthesis. For the latter approach, forests of carbon nanotubes are considered as particularly promising templates, with respect to their one dimensional nature and the resulting high surface area. In this work, w…
Tuning the surface energy of fluorinated diamond-like carbon coatings via plasma immersion ion implantation plasma-enhanced chemical vapor deposition with 1,1,1,2-tetrafluoroethane
We report the fabrication of electrically functional polyaniline thin-film microdevices. Polyaniline films were printed in the solid phase by Laser Induced Forward Transfer directly between Au electrodes on a Si/SiO2 substrate. To apply solid-phase deposition, aniline was in situ polymerized on quartz substrates. Laser deposition preserves the morphology of the films and delivers sharp features with controllable dimensions. The electrical characteristics of printed polyaniline present ohmic behavior, allowing for electroactive applications. Results on gas sensing of ammonia are presented.
Oblique angle deposition of oxides is being famous for fabricating inhomogeneous thin films with variation of refractive index along thickness in a functional form. Inhomogeneous layers play a key role in the development of rugate interference devices for photo-physical applications. Such obliquely deposited thin films show high porosity which is a critical issue related to their mechanical and environmental stability. Hence, it is important to investigate elastic properties of such film in addition to optical properties. Using atomic force acoustic microscopy, we report indentation modulus of…
Nanostructures of Titanium oxide (TiO2) are being studied for many promising applications, e.g., solar photovoltaics, solar water splitting for H2 fuel generation etc., due to their excellent photo-catalytic properties. We have synthesized low-dimensional TiO2 nanoparticles by gas phase CW CO2 laser pyrolysis. The laser synthesis process has been optimized for the deposition of highly pure, nearly mono-dispersed TiO2 nanoparticles on silicon substrates. Hard x-ray standing wave-field (XSW) measurements in total reflection geometry were carried out on the BL-16 beamline of Indus-2 synchrotron r…
The effects of substrate treatment, temperature and composition on the surface morphology of Ni-Cr thin films grown on MgO(001) are studied by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). A combination of acid-etching and high temperature deposition (400C) will result in smooth films and terraces (up to 30 nm wide) suitable for the study of progression of chemical reactions on the surface. Two different treatments are used to prepare the MgO substrates for deposition and they introduce characteristic differences in film surface morphology. Thin films that are grown on…
The functional properties of devices based on perovskite oxides depend strongly on the growth modes that dramatically affect surface morphology and microstructure of the hetero-structured thin films. To achieve atomically flat surface morphology, which is usually a necessity for the high quality devices, understanding of the growth mechanism of heteroepitaxial thin film is indispensable. In this study, we explore heteroepitaxial growth kinetics of the SrRuO3 using intermittent growth scheme of pulsed laser epitaxy and ex-situ atomic force microscopy. Two significant variations in surface rough…
We present a study of the synthesis of epitaxial V$_2$O$_3$ films on $c$-plane Al$_2$O$_3$ substrates by reactive dc-magnetron sputtering. The results reveal a temperature window, at substantially lower values than previously reported, wherein epitaxial films can be obtained when deposited on [0001] oriented surfaces. The films display a metal-insulator transition with a change in resistance of up to four orders of magnitude, strongly dependent on the O$_2$ partial pressure during deposition. While the electronic properties of the films show sensitivity to the amount of O$_2$ present during de…
Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance for technological applications in interdisciplinary fields such as biotechnology, medicine and advanced materials. Here we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (n…
The nucleation mechanisms during solution deposition of organic semiconductor thin films determine the grain morphology and may influence the crystalline packing in some cases. Here, in-situ optical spectromicroscopy in reflection mode is used to study the growth mechanisms and thermal stability of 6,13-bis(trisopropylsilylethynyl)-pentacene thin films. The results show that the films form in a supersaturated state before transforming to a solid film. Molecular aggregates corresponding to subcritical nuclei in the crystallization process are inferred from optical spectroscopy measurements of t…
Copper oxide thin films are deposited on quartz substrates by DC magnetron sputtering and the effect of deposition temperature on their optoelectronic properties is examined in detail. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) analysis, Raman spectroscopy, UV-Vis spectroscopy, and four-probe sheet resistance measurements are used to characterize the surface morphology, structural, optical, and electrical properties respectively. Deposition is carried out at room temperature and between 200 and 300 °C. XRD analysis indicates that the oxide formed is primarily Cu$_2$O and the a…
We present a new network modeling approach for various thin film growth techniques that incorporates re-emitted particles due to the non-unity sticking coefficients. We model re-emission of a particle from one surface site to another one as a network link, and generate a network model corresponding to the thin film growth. Monte Carlo simulations are used to grow films and dynamically track the trajectories of re-emitted particles. We performed simulations for normal incidence, oblique angle, and chemical vapor deposition (CVD) techniques. Each deposition method leads to a different dynamic ev…
During the growth of metal thin films on dielectric substrates at a given deposition temperature T, the film's morphology is conditioned by the magnitude and asymmetry of up- and downhill diffusion. Any severe change of this mechanism leads to a growth instability, which induces an alteration of the thin film morphology. In order to study this mechanism, ultra-thin Pt films were deposited via pulsed laser deposition (PLD) onto yttria-stabilized-zirconia single crystals at different deposition temperatures. The morphological evolution of Pt thin films has been investigated by means of scanning …
We show that in the construction of continuum equations for competitive growth processes that are a mixture of random deposition and a correlation process, a distinction must be made within a \textit{single universality class} between depositions that do and do not create voids in the bulk. Within these subclasses the bulk morphology is reflected in the surface roughening via \textit{nonuniversal} prefactors in the universal scaling of the surface width.
An experimental study was conducted on controlling the growth mode of La0.7Sr0.3MnO3 thin films on SrTiO3 substrates using pulsed laser deposition (PLD) by tuning growth temperature, pressure and laser fluence. Different thin film morphology, crystallinity and stoichiometry have been observed depending on growth parameters. To understand the microscopic origin, the adatom nucleation, step advance processes and their relationship to film growth were theoretically analyzed and a growth diagram was constructed. Three boundaries between highly and poorly crystallized growth, 2D and 3D growth, stoi…
We report on sexithiophene films, about 150nm thick, grown by thermal evaporation on single crystal oxides and, as comparison, on Si/SiO2. By heating the entire deposition chamber at 100 C we obtain standing-up oriented molecules all over the bulk thickness. Surface morphology shows step-like islands, each step being only one monolayer height. The constant and uniform warming of the molecules obtained by heating the entire deposition chamber allows a stable diffusion-limited growth process. Therefore, the regular growth kinetic is preserved when increasing the thickness of the film. Electrical…
