Changing Substrate Temperature Research Articles

Continuous strain-mediated perpendicular magnetic anisotropy in epitaxial (111) CoFe2O4 thin films grown on LiTaO3 substrates

Perpendicular magnetic anisotropy (PMA) in magnetic thin films has attracted much attention due to its potential applications in spintronics devices. Here, we report the continuous strain-mediated PMA in epitaxial (111) CoFe2O4 (CFO) thin films grown on (0001) LiTaO3 substrates. A large variation in lattice strain (∼0.9%) in a continuous way is realized in the CFO thin films by changing substrate temperature during deposition due to the difference in the thermal expansion coefficient between CFO and LiTaO3. As a result, the PMA of the (111) CFO thin films can be continuously mediated by the strain with uniaxial magnetic anisotropy energy in the range of 0.12-14.69×106 erg/cm3. Furthermore, the strain as well as the consequent PMA in the (111) CFO thin films can be maintained within the thickness of 25–205 nm, which is consistent with the scenario of the magnetoelastic effect. Our results reveal that the CFO/LiTaO3 system can be regarded as an ideal platform to realize robust PMA and its continuous strain tuning in the (111) CFO thin films by virtue of strain-induced magnetic anisotropy.

Effect of changing substrate temperature of PbI2 thin films deposited by spray technique on the structural ,optical and electrical properties

تم تحضير طبقات متعددة الكريستالات من يوديد الرصاص باستخدام تقنية الرش على ركائز زجاجية للتطبيق المحتمل في الكشف النووي. درس هذا البحث تأثير تغير درجة حرارة الركيزة لأغشية PbI2 على الخصائص التركيبية والبصرية والكهربائية عند درجات حرارة مختلفة للركيزة ( 150.200.250) درجة مئوية.

Effects of substrate temperature on the growth of CuO nano/micro rods by ion beam sputter deposition

CuO nano/micro rods were deposited on Si substrates by ion beam sputter deposition at substrate temperatures 300 °C, 350 °C, 400 °C and 450 °C. The effects of changing substrate temperature on the structural properties and surface morphology of the deposited CuO nano/micro rods were studied. Field Emission Scanning Electron Microscopy micrographs showed that at substrate temperature of 300 °C and 350 °C, tiny nanoparticles were observed on the surface of CuO thin films and at substrate temperature of 400 °C and 450 °C, CuO nano/micro rods of lengths (100 nm to 1 μm) and diameters (25 nm to 30 nm) observed in a periodic arrangement. X-Ray Diffraction (XRD) analysis showed that all the diffraction peaks of the samples were single-crystalline CuO corresponded to () orientation. From the crystallographic analysis using XRD data, crystallite sizes of the samples increased (18 to 32 nm) with the increase of substrate temperature. The Micro-Raman spectroscopy investigation shows that all the Raman peaks observed were phonon modes of CuO and as the substrate temperature increased, the intensities of the Rama peaks increased. Hence, by changing substrate temperatures, it is possible to deposit high quality CuO nano/micro thin films with tunable structures, morphologies and sizes for different optoelectronic applications through ion beam sputter deposition.

Effects of Process Parameters on the Microstructural Characteristics of DC Magnetron Sputtered Molybdenum Films on Graphite Substrate

Graphite, due to its extreme purity and high-temperature stability, is considered as the material of choice for nuclear fusion reactors. However, it undergoes rapid oxidation and erosion at extreme environmental conditions like those experienced by the plasma-facing components (PFCs) of a fusion reactor. On the other hand, molybdenum (Mo) does offer a combination of thermal, mechanical, and chemical properties that make it an aspirant candidate for PFCs and other applications demanding substantial physical, chemical, and thermal stability as well as significant thermal conductivity. Mo films on graphite is one of the attractive options to sustain against such harsh environmental conditions. Here, in this work, we develop Mo films over graphite substrate through sputter deposition and analyze the effects of process parameters like the sputter power and the substrate temperature on the morphology and film quality. It is shown that an increase in sputter power, as well as substrate temperature, induces significant changes in the topography of the films. For low-temperature depositions, the grain morphology does not change with increasing sputter power, however, for relatively higher substrate temperatures, significant changes in morphology are observed with increasing sputter power. Similarly, dependences of crystallite size, film roughness, and electrical conductivity are discussed with changing sputter power and substrate temperature. Our results suggest that the kinetic energy of the sputtered Mo particles plays a crucial role in determining the final film quality. This study manifests that optimum sputter parameters guarantee quality Mo films over graphite substrate.

Multipass and reciprocating microwear study of TiN based films

Titanium nitride (TiN) coatings with a Cr metallic interlayer were deposited on AISI 316L stainless steel substrates using D. C. unbalanced magnetron sputtering, changing substrate temperature and gas mixture. The effect of the sliding motion in wear tests was studied, comparing multipass (unidirectional) and reciprocating (bidirectional) sliding modes. In addition, microstructure, mechanical properties and adhesion were analyzed. The structural characterization was performed by scanning electronic microscopy (SEM) and grazing incidence X-ray diffraction (GIXRD). Moreover, hardness of the coating was measured by spherical nanoindentation, and thermal residual stresses were estimated. The scratch tests were conducted using a steel ball of 1 mm of diameter. To study the effect of sliding motion, the wear tests were carried out with an alumina ball of 3 mm of diameter, in both sliding modes the same linear test geometry, a stroke length of 3 mm and loads of 0.5 and 1 N were used. TiN coatings thicknesses ranged from 1.1 to 1.8 μm, growing in preferred orientations (200) and (111). It was found that increasing the nitrogen content during the deposition cause a decrease in the adhesion of the coating. In the sliding wear tests, the coefficient of friction (COF) values ranged from 0.12 and 0.22. The effect of sliding motion in COF was more evident in the tests performed with 0.5 N load, reciprocating exhibited higher values than multipass. The specific wear coefficients k varied from 6.9 × 10−4 to 1.88 × 10−3 mm3 · N−1m−1 for all tests, the highest value was obtained in a reciprocating test.

Detailed Structural and Morphological Characterization of InGaN Thin Films Grown by RF Magnetron Sputtering with Various Substrate Temperature

Indium Gallium Nitride thin film was successfully grown on the substrate using an RF magnetron sputter under condition of different substrate temperatures. Various experimental measurements were taken to understand effect of substrate temperature on the structure of thin film and results were analyzed. Grazing mode of XRD results confirmed that thin film has a hexagonal structure with plane for and substrate temperature. It was seen that structural parameters of thin film show a change with substrate temperature change. Reasons were discussed. Strain and stress values in thin film were calculated from experimental results and it was found that all thin film has compressive stress. Morphological parameters of thin film were measured by AFM and it was understood that these properties are varied by changing substrate temperature. Also, growth mode of some thin film was found to be layer-plus-island mode (Stranski-Krastanov growth mode), others was found to be layer by layer growth mode (Frank van der Merwe mode). SEM analysis gives that increasing substrate temperature worsened the surface structure of thin film; it is compatible with and supports XRD results. Compositional values in thin film were found from XPS analysis. In addition to our material, carbon and oxygen have also been obtained from XPS results, as expected. Detailed structural and morphological properties of thin film have been seen to change by changing substrate temperature and we believe this may play an important role in the production of based optoelectronic devices.

Control of Domain Structures in Multiferroic Thin Films through Defect Engineering.

Domain walls (DWs) have become an essential component in nanodevices based on ferroic thin films. The domain configuration and DW stability, however, are strongly dependent on the boundary conditions of thin films, which make it difficult to create complex ordered patterns of DWs. Here, it is shown that novel domain structures, that are otherwise unfavorable under the natural boundary conditions, can be realized by utilizing engineered nanosized structural defects as building blocks for reconfiguring DW patterns. It is directly observed that an array of charged defects, which are located within a monolayer thickness, can be intentionally introduced by slightly changing substrate temperature during the growth of multiferroic BiFeO3 thin films. These defects are strongly coupled to the domain structures in the pretemperature-change portion of the BiFeO3 film and can effectively change the configuration of newly grown domains due to the interaction between the polarization and the defects. Thus, two types of domain patterns are integrated into a single film without breaking the DW periodicity. The potential use of these defects for building complex patterns of conductive DWs is also demonstrated.

Effects of substrate temperature and deposition rate on the phase separated morphology of co-sputtered, Cu-Mo thin films

We report on the evolution of phase-separated morphologies in co-sputtered Cu-Mo films as a result of varying substrate temperature and deposition rate during deposition. A transition from vertically-oriented concentration modulations to laterally-oriented modulations followed by randomly-oriented modulations was observed in the Cu-Mo films because of changing substrate temperature at constant deposition rate. A refinement of the Cu-Mo domains was observed at increasing deposition rate at a constant substrate temperature. A coarsening of phase-separated domains was also observed with increasing substrate temperature. The phase separation kinetics that controlled film morphology were limited by the surface interdiffusion of each species as the film grew in thickness. Control over the surface interdiffusion length was achieved by altering the deposition temperature and material flux.

Control the crystal growth of Al-doped ZnO thin film prepared by pulsed laser deposition and the influences on its optical and electrical properties

In this work, highly transparent and highly conductive thin films of Al-doped ZnO (AZO) are achieved by pulsed laser deposition (PLD). By changing substrate temperature in the range of room temperature to 500°C during the deposition process, the preferential growth direction of AZO crystal is controlled and, therefore, the surface morphology, optical and electrical properties of AZO thin films are able to be manipulated. X-ray diffractograms as a function of the substrate temperature clearly illustrate the ability to control the preferential growth direction of AZO. At the low substrate temperature, the growth along [002] direction corresponding to c-axis of hexagonal ZnO is only observed. By elevating the substrate temperature, not only crystallinity of AZO thin film is further improved but also the competition of crystal growth along the [002], [001] and [101] directions are occurred due to the increase of total energy and surface mobility of cluster/atom. The AZO films obtained by all preparation conditions exhibit an n-type semiconducting characteristics, furthermore, the carrier concentration and the carrier mobility of AZO thin films can be optimized to reach 4.10×1020 cm-3 and 7.53 cm2/Vs, respectively. The excellences in both carrier concentration and mobility of AZO thin film lead to very low resistivity of 2.08×10-3 Ωcm. In addition, the wide optical band gap of ∼3.50 eV together with the high transparency over 90% in visible region is obtained from the AZO thin films. The exceptional optical and electrical properties of AZO thin film demonstrate that such material has enough potential to become a promising candidate using in optoelectronic applications.

Interfacial reactions in SiCf/C/Ti17 composites dominated by texture of carbon coatings

Two kinds of turbostratic carbon coatings with different texture were deposited on SiC fibers using single filament chemical vapor deposition by changing substrate temperature: 920 and 1000 °C, labeled as C920 and C1000, respectively, followed by coating Ti17 matrix, and then SiCf/C920/Ti17 and SiCf/C1000/Ti17 composites were fabricated by hot isostatic pressing (HIP). C1000 possesses much stronger texture than C920, evidenced by combined tests of X-ray photoelectron spectrum, Raman spectroscopy and transmission electron microscope (TEM). Interfacial reactions of SiCf/C920/Ti17 and SiCf/C1000/Ti17 composites are found to depend strongly on texture of turbostratic carbon coatings after HIP, revealing that C1000 with stronger texture can hinder the outward diffusion of C and inward diffusion of matrix elements more efficiently than C920, which is elucidated by the results of scanning electron microscope, TEM and energy-dispersive spectroscopy. Interdiffusion between C coating and Ti17 matrix results in formation of C gradient distribution in interfacial reaction layer for both composites, in which interfacial zone of fiber and matrix can be described as turbostratic C||amorphous C||fine-grained TiC||transition TiC||coarse-grained TiC, however, each sub-layer thickness is determined by the texture of C coating. Based on these results, the model of interfacial reactions dominated by texture of C coatings was proposed.

High tunable BaSnxTi1-xO3 thin films for microwave applications

ABSTRACTThin films of BaSnxTi1-xO3 composition (Sn/Ti ≈50/50) are grown in-situ by RF magnetron deposition onto Pt/Ti/Al2O3 substrate. Structural and dielectric properties are optimized by changing substrate temperature. Best thin-film samples have shown a high tunability (about 3.5) and low dielectric losses attractive for microwave electronics.

Reducing Spatial Heterogeneity of MALDI Samples with Marangoni Flows During Sample Preparation.

This work demonstrates a method to prepare homogeneous distributions of analytes to improve data reproducibility in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Natural-air drying processes normally result in unwanted heterogeneous spatial distributions of analytes in MALDI crystals and make quantitative analysis difficult. This study demonstrates that inducing Marangoni flows within drying droplets can significantly reduce the heterogeneity problem. The Marangoni flows are accelerated by changing substrate temperatures to create temperature gradients across droplets. Such hydrodynamic flows are analyzed semi-empirically. Using imaging mass spectrometry, changes of heterogeneity of molecules with the change of substrate temperature during drying processes are demonstrated. The observed heterogeneities of the biomolecules reduce as predicted Marangoni velocities increase. In comparison to conventional methods, drying droplets on a 5 °C substrate while keeping the surroundings at ambient conditions typically reduces the heterogeneity of biomolecular ions by 65%-80%. The observation suggests that decreasing substrate temperature during droplet drying processes is a simple and effective means to reduce analyte heterogeneity for quantitative applications. Graphical Abstract ᅟ.

Manipulation of Cell Proliferation and Migration Employing Surface Acoustic Waves and Hydrophobic/Hydrophilic Structured Substrates

Tissue engineering for the purpose of nerve or spinal cord repair has become an emerging topic in biophysical and medical research. Addressing this issue relies on an understanding of the principles of tissue growth and applying this understanding to produce functional replacement tissues for clinical use after injury. During wound healing, the damaged tissue layer is reassembled and regenerated through cell proliferation and migration. Thus, any type of external stimuli being able to improve this process of cell regeneration could be highly useful for accelerating wound repair. To study such an external wound healing parameter, we use surface acoustic waves (SAW) for dynamic in vitro manipulation of living cells in a precise controlled manner. In our investigations, we use osteoblastic SaOs-2 cells on a Si02-covered piezoelectric LiNbO3 substrate which we irradiate with SAW continuously for 72hours. Employing a conventional wound healing assay, we show the SAW - treated cells exhibit significantly increased proliferation and migration, respectively, as compared to control samples. Apart from quantifying our experimental findings, we also demonstrate the biocompatibility and biofunctionality of our SAW reactor by using LDH assays. We can neglect parasitic or beneficial side effects such as changing substrate temperature or nutrient flow rate through (OR ‘by closely’) monitoring the temperature and flow field using infrared microscopy and micro particle image velocimetry. Indeed, our results show that the SAW-induced dynamic, mechanical, and electrical stimulation directly promotes cell growth by increasing cell regeneration and migration rates. Our next goal is to guide the cells along certain tracks using hydrophobic/hydrophilic trails in combination with SAW.

The improvement of high-frequency magnetic properties in oriented hcp-Co78Ir22 soft magnetic films fabricated at high substrate temperature

The c-axis oriented hcp-Co78Ir22 soft magnetic thin films with in-plane uniaxial anisotropy and negative magnetocrystalline anisotropy were fabricated with substrate temperature at 30°C and 500°C, respectively. Our results further reveal that sputtering under 500°C can obtain a film with better grain structure and higher degree of orientation, which in turn improves the Ms and the magnetocrystalline anisotropy field. As the Ms and the total out-of-plane anisotropy field including the demagnetization field and the magnetocrystalline anisotropy field were enhanced, the high-frequency magnetic parameter (μi−1)fr is approximately two times larger than that of the sample fabricated at 30°C. In addition, the damping constant decreases quite a lot with increasing temperature. This work indicates that the high frequency properties can be well adjusted by changing substrate temperature.

スパッタ薄膜の内部応力に及ぼす基板温度の影響

In our recent research, it was found that the effects of ion bombardment for thin films can be estimated using the ion bombardment parameter Pi. Internal stress in sputtered thin films can be classified into thermal stress and true stress. In this study, the internal stress in thin films was evaluated by the changes in evaporant sources (Ni or Al), substrate (Si or glass), and substrate temperature during the deposition. Internal stress in thin films with ion bombardment as a part of true stress was controlled by plasma diagnostics. Thermal stress in the thin films was evaluated from the thermal expansion coefficient of the films and the substrate with the changing substrate temperature during thin film deposition. It was found that internal stress of the films was strongly dependent on thermal stress. Despite the control of ion bombardment by plasma diagnostics, the values of true stress for the films were not continuous. This suggests that in addition to ion bombardment, true stress is also governed by microstructural changes with changing substrate temperature.

Improvement in n-ZnO/p-Si diode properties using ZnO/AZO homogeneous metal contact

In this study, an n-ZnO/p-Si diode with a ZnO/AZO homogeneous metal contact was fabricated and compared with a ZnO/Al metal contact. AZO films were deposited using atomic layer deposition (ALD). Prior to the device fabrication, the AZO films were optimized in terms of their characteristic as TCO on a soda lime glass. Their resistivity is 1.08 × 10−3 Ω·cm and their transmittance is over 80% in the visible light region for a 5% Al doping concentration. The leakage current of ZnO/AZO homogeneous contact diodes is lower than that of ZnO/Al devices. In addition, under thermal stress induced by changing substrate temperature from 300 to 450 K, the contact resistance of the ZnO/AZO structure is more stable than that of the ZnO/Al structure.

Improvement of critical current densities in SmBa2Cu3Oy, films with BaHfO3 nano-rods using low temperature growth technique

We studied growth substrate temperature dependent morphologies of BaHfO3 (BHO) nano-rods for SmBa2Cu3Oy, (SmBCO) films with BHO fabricated by pulsed laser deposition (PLD) method. The morphology of BHO nano-rods within the SmBCO matrix could be controlled by changing substrate temperatures adoping a Low Temperature Growth (LTG) technique. Using the LTG technique, we could fabricate SmBCO films showed c-axis orientation even at low substrate temperature during deposition without a degradation of superconducting properties, which is one of the most advantages of the LTG technique. In this study, we found an optimal morphology of the BHO nano-rods and the morphology was fine, straight and various growth directions. The BHO nano-rods were more effective to improve the Jc in a magnetic field than other morphologies of the BHO nano-rods.

Effect of substrate temperature on microstructure and optical properties of single-phased Ag2O film deposited by using radio-frequency reactive magnetron sputtering method

Using a radio-frequency reactive magnetron sputtering technique, a series of the single-phased Ag2O films are deposited in a mixture of oxygen and argon gas with a flow ratio of 2:3 by changing substrate temperature (Ts). Effects of the Ts on the microstructure and optical properties of the films are investigated by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. The single-phased Ag2O films deposited at values of Ts below 200 °C are (111) preferentially oriented, which may be due to the smallest free energy of the (111) crystalline face. The film crystallization becomes poor as the value of Ts increases from 100 °C to 225 °C. In particular, the Ag2O film deposited at Ts = 225 °C loses the 〈111〉 preferential orientation. Correspondingly, the film surface morphology obviously evolves from a uniform and compact surface structure to a loose and gullied surface structure. With the increase of Ts value, the transmissivity and the reflectivity of the films in the transparent region are gradually reduced, while the absorptivity gradually increases, which may be attributed to an evolution of the crystalline structure and the surface morphology of the films.

Formation of NiZn ferrite nano-crystalline thin films by rf magnetron sputtering with changing substrate temperatures

Thin films of NiZn ferrite, Ni0.5Zn0.5Fe2O4, were formed on the substrate of quartz glass plate by rf magnetron sputtering by changing the substrate temperatures during the sputtering from 200 to 700°C. The size of the NiZn ferrite crystallites composing the film was exhibited to be controlled from less than 10nm to about 40nm by the change of the substrate temperature. The formed nano-crystalline NiZn ferrite thin film with the crystalline size of ∼40nm showed constant magnetic permeability up to ∼2GHz, indicating the possibility of nano-crystalline ferrite thin films as the materials for magnetic devices workable in GHz-frequency region.

Crystalline phase in Alq3 films grown by the hot-wall method

We deposited tris-(8-hydroxyquinoline) aluminum (Alq3) films on glass substrates by using the hot-wall method. The Alq3 films were deposited for changing substrate temperature from 50 to 125°C. With increasing the substrate temperature, anomalous growth patterns with a butterfly-like shape appeared and spread on the surface of the deposited films. The intensity of emission from the anomalous region is stronger than that from the smooth region as found by fluorescence microscope observations and photoluminescence measurements. The observed anomalous growth in the films deposited at high substrate temperatures was identified to be due to α-phase crystallization of Alq3 from the emission spectrum and X-ray diffraction measurements and from comparing those results with α-Alq3 crystals grown by the vapour phase growth technique.