Cr Thin Films Research Articles

Surface Morphology of ZnGa2O4:Cr Thin Films Obtained by RF Ion-Plasma Sputtering

Surface Morphology of ZnGa2O4:Cr Thin Films Obtained by RF Ion-Plasma Sputtering

Crack Development and Electrical Degradation in Chromium Thin Films Under Tensile Stress on PET Substrates

The mechanical and electrical deterioration of chromium (Cr) thin films sputtered onto polyethylene terephthalate (PET) substrates under tensile strain was studied. Understanding mechanical and electrical stability due to imposed strain is particularly important for device reliability, as the demand for flexible electronic devices increases. Cr thin films, widely spread across the field of electronic and sensor applications, face crack propagation with electrical degradation with tensile stress that can seriously compromise the performance. Accordingly, this study offers new findings on how Cr film thickness might influence crack formation and electrical resistance differently and also the general guidelines for flexible electronic component design with respect to long-term durability. Electrical resistances were measured while mechanically stretching 100- and 200 nm thin sheets. The study focused on crack development and propagation mechanisms in both film thicknesses and their effects on percentage change in electrical resistance (PCER). Scanning electronic microscopy (SEM) was used to characterize surface morphology and observe cracks as the strain rose. Early crack formation in 100 nm Cr films led to rapid PCER increases due to quick crack propagation and fast electrical degradation. Thicker 200 nm films, however, showed a more gradual PCER rise with fewer but deeper cracks, indicating a regulated strain response. Unlike the sharp PCER spike in 100 nm films, 200 nm samples were more variable, with three out of four showing a slight PCER decrease at the end, hinting at partial crack repair or conductive realignment before full failure. These results underscore the role of layer thickness in managing crack propagation and electrical stability, relevant for flexible electronics and strain sensors. This paper is aligned with the ninth goal of the United Nations Sustainable Development Goals, specifically Target 9.5: Enhance Research and Upgrade Industrial Technologies.

Effect of different metallic doping elements on the physical properties of iron oxide thin films

This study investigates the physical properties of pure and Co, Cr, Mn, and Ni-doped Fe2O3 thin films fabricated using spray pyrolysis techniques on glass substrates. The primary aim is to understand how doping influences the structural, optical, and dielectric properties of Fe2O3 thin films. The deposition parameters were kept constant for all samples, with a fixed dopant concentration of 3 weight percent (wt%). X-ray diffraction (XRD) analysis revealed a single diffraction peak indexed as (104), decreasing in crystallite size from 17.27 nm for the pure film to approximately 11.5 nm for all doped films. Field emission scanning electron microscopy (FE-SEM) images displayed non-homogeneous grain formation, characterized by an average grain size larger than the crystallite size, indicating agglomeration. The optical band gap value shifted from 2.54 eV for the pure film to higher values upon doping with various elements, signifying direct allowed transitions. Changes in refractive index dispersion with wavelength were observed based on the dopant type. The application of the Spitzer-Fan model revealed an increase in high-frequency dielectric constant upon doping compared to the pure film, varying across different dopants. Photoluminescence (PL) spectra recorded under excitation at 340 nm exhibited multiple emission peaks within the spectral range of 399 to 600 nm.

High-performance virtual sensors array based on a single-chip FBAR for volatile organic compounds (VOCs) detection and classification

The detection and classification of volatile organic compounds (VOCs) are of great significance in atmospheric environment monitoring and have garnered extensive attention in recent decades. This study proposes a virtual sensor array (VSA) for VOC detection and classification fabricating a single-chip high-Q-factor film bulk acoustic resonator (FBAR) functionalized with MIL-101(Cr) thin film, known for its porous crystal structure and high specific surface area. The sensing performance of five different VOCs was evaluated to characterize the VOCs, achieving high detection accuracy calibrated with the Langmuir adsorption model. The FBAR’s frequency response was utilized to determine the sensitivity and limit of detection (LOD), yielding sensitivity and LOD of 85.45 Hz/ppm and 51 ppm, respectively, for isopropanol. The identification and classification capabilities of the proposed VSA for VOCs and their mixtures were assessed using statistical methods and machine learning algorithms, realizing classification accuracies of 100 % for pure VOCs and 94.6 % for mixtures. The developed VSA demonstrates superior performances in VOC detection and classification, with potential applications across various domains.

Fabrication of microchannels and through-holes in Borofloat glass using Cr thin film with positive photoresist as the masking layer through wet etching

The present work investigates the efficiency of the masking layer, composed of Cr thin film and positive photoresist (AZ1512HS), to fabricate microchannels and through-holes in Borofloat glass wafers via wet etching, utilizing 20 % HF. The initial phase of the work emphasizes microchannel fabrication. ∼50 µm deep and well-defined microchannels are accomplished with no discernible surface defects on the wafer. In the later phase, predominantly sharp-edged through-holes are successfully fabricated in the wafer, without any observable pinholes, during etching for 300 min. The masking layer constantly exhibited robust adhesion to the wafer throughout the etching process, affirming its effectiveness. This work demonstrates the first instance of fabricating 500 µm deep through-holes in glass with Cr thin film and photoresist as a masking layer.

Hot probe technique for thin films Seebeck coefficient measurement

A new experimental method using a 50 μm diameter hand fabricated hot probe of Pt90/10Rh alloy is proposed as a tool to measure the Seebeck coefficient of thin films deposited onto electrically insulated substrates. A thermal model for heat transfer inside the probe and to the sample was developed to simulate the corresponding temperature distributions. Simulations showed that the ratio of the temperature rise in the contact point to the average temperature of the probe evolves basically independent on electrical current and film-substrate properties. Moreover, the values of contact radius and thermal contact resistance should not be necessary known, but only the pairs which are best fitting the probe thermal resistance in contact with the film-substrate. This brings a great simplification in respect with certain AFM based hot probe methods for which is necessary to determine these two parameters by calibration of the two substrates with known thermal conductivity. The values can be further used to evaluate the Seebeck coefficient of the sample with a macroscopic probe, within 1 % precision. By variance to the classical measuring methods, which resort to a heater-heat sink ensemble instrumented with thermocouples, heated metallic rods with built-in thermocouples or microfabricated structures, the proposed method is fast, reliable and of higher spatial resolution. The method was validated by measuring the Seebeck coefficient on CdS, Bi and Cr thin films reference samples, respectively.

Microstructures, electrical and mechanical properties of the magnetron sputter deposited metal thin films at variable angles

In this work, we investigate the microstructures, mechanical and electrical properties of the Cr, Fe, Ni, Cu, and Al thin films that were grown by using magnetron sputtering at various angles. The relationships among the electrical and mechanical properties (resistivity, nanoindentation hardness, and modulus), structural parameters (domain size, thickness, column angle), and sputter deposition conditions (flux angle, deposition rate) were investigated through the Pearson correlation analysis. Electrical resistivity was found to be significantly affected by both the domain size and the deposition rate. A strong correlation between hardness and domain size was observed. However, Young's moduli did not exhibit a correlation within the investigated parameter space.

Critical slowing of the spin and charge density wave order in thin film Cr following photoexcitation

Critical slowing of the spin and charge density wave order in thin film Cr following photoexcitation

The contradictory feather of Cr thin film compressive residual stress generation under energetic depositions

Ion bombardment is an important approach to generate thin film compressive residual stress independent of film growth through energetic deposition. In this study, a series of Cr/Si(100) thin films were energetically deposited using Modulated Pulsed Power Magnetron Sputtering (MPPMS) to learn the residual stress variation. The steady residual stress of Cr/Si(100) thin films, ex-situ characterized based on Stoney’s equation, exhibited a compressive nature with the maximum stress observed at approximately 100–150°C as the substrate temperature increased to 220°C. The steady residual stress variation was inconsistent with calculated thermal stress and intrinsic growth stress, and the calculated compressive stress for the adatom insertion and ion bombardment are contradictory under varied temperatures. The ability of adatom movement and insertion to grain boundaries promote the formation of compressive stress, while the defect annihilation and atom rearrangement inhibit the ion bombardment-induced residual stress.

The influence of deposition conditions on the surface morphology and luminescent properties of (Y0.06Ga0.94)2O3:Cr thin films

Thin films of (Y0.06Ga0.94)2O3:Cr were obtained by radio-frequency (RF) ion-plasma sputtering in an argon atmosphere on polycrystalline polycor and amorphous υ-SiO2 substrates. The surface morphology of the films was studied by atomic force microscopy. It was found that during argon annealing of (Y0.06Ga0.94)2O3:Cr thin films on υ-SiO2 substrates, grain growth occurs perpendicular to the substrate surface. The results of studies of the photoluminescence and cathodoluminescence luminescence of the investigated films are presented. It is shown that thin films of (Y0.06Ga0.94)2O3:Cr on υ-SiO2 substrates under photoexcitation emit in the blue region of the spectrum and this luminescence is due to the luminescence of the (Y0.06Ga0.94)2O3 matrix. Under cathodic excitation, the activator luminescence of the Cr3+ ion dominates with a maximum in the region around 700 nm, due to the electronic transitions 4T2 → 4A2.

Effect of preparation conditions on the surface morphology and edge absorption of ZnGa2O4:Cr thin films

Thin ZnGa2O4:Cr films were obtained by RF ion-plasma sputtering in argon and argon-oxygen atmospheres mixtures on single-crystal NaCl and amorphous υ-SiO2 substrates. The surface morphology of the films was studied by atomic force microscopy. It was found that during the annealing of ZnGa2O4:Cr films on υ-SiO2 substrates in oxygen, the grains forming the film grow along the film surface, and during annealing in an argon atmosphere, the growth of grains is observed normal to the film surface. The region of the fundamental absorption edge was studied by optical spectroscopy. The variation of the optical band gap of Eg depending on the deposition and annealing atmosphere was determined. The total effective mass of free charge carriers and the concentration of free charge carriers are estimated. It is shown that the shift of the fundamental absorption edge in ZnGa2O4:Cr thin films after annealing in an argon atmosphere and when oxygen is added to the sputtering atmosphere is due to the Burstein-Moss effect.

Improved Thermal Stability of Al-Si Alloy Coated Steel Sheet with Cr Thin Film Deposition

We investigated the effect of Cr thin film deposition on the thermal stability and corrosion resistance of hot-dip aluminized steel. A high-quality Cr thin film was deposited on the surface of the Al-9 wt. % Si-coated steel sheets by physical vapor deposition. When the Al-Si coated steel sheets were exposed to a high temperature of 500℃, Fe from the steel substrate diffused into the Al-Si coating layer resulting in discoloration. However, the highly heat-resistant Cr thin film deposited on the Al-Si coating prevented diffusion and surface exposure of Fe, improving the heat and corrosion resistances of the Al-Si alloy coated steel sheet.

Comparative study of titanium and chromium transition layers on quartz substrates

As an important functional material, quartz needs to be firmly welded with electrodes through a transition layer—such as a Ti or Cr film—for practical applications. It is important to understand the microstructure of the transition layer and its interfacial structure with quartz to improve the reliability of corresponding devices. The present authors conducted a systematic comparative study on Ti and Cr thin films deposited on the surface of quartz. The distribution and valence of elements on the film–substrate interface were analyzed by X-ray photoelectron spectroscopy. The grain size and defect distribution in the films, as well as the morphology and composition distribution at the film–substrate interface, were characterized by transmission electron microscopy in combination with energy-dispersive spectrometry. The phase and preferred orientation of the films were measured by X-ray diffraction. The bonding force between the Ti and Cr films and quartz was investigated through nanoscratch experiments. Fracture analysis of the delaminated films was carried out by Auger electron spectrometry. Substantial chemical bonding was generated at the Ti–quartz interface, and there were no detectable micro-defects, resulting in high bonding strength. During deposition of the Cr film, there was substantial atomic peening, resulting in a nanoscale damage layer on the surface of quartz, facilitating delamination in scratch experiments.

Influence of magnetic field strength on plasma, microstructure, and mechanical properties of Cr thin films deposited by MPPMS and DOMS

Magnetic field strength plays a vital role in determining the discharge behavior in magnetron sputtering. It enables the customization of discharge plasma and thin film properties. This study aims to compare the discharge behavior and investigate the potential effects on Cr thin films deposited using modulated pulsed power magnetron sputtering (MPPMS) and deep oscillation magnetron sputtering (DOMS) at different magnetic field strengths. The magnetic field strength in the target center increased from 67 to 91 mT tuning by the target thickness from 8 to 3 mm, and the average electron temperature was higher in a DOMS discharge than that in a MPPMS discharge. For both MPPMS and DOMS deposited Cr thin films, the refractive index and mechanical properties have been promoted with the increase in magnetic field strength, and almost all Cr thin films showed a Cr(110) preferred orientation. The hardness and modulus increased from 11.3 and 275.6 to 13.8 to 285.1 GPa for MPPMS deposited thin films, while the hardness and modulus for DOMS Cr thin films were much higher, increasing from 11.2 and 283.6 to 17.3 to 297.2 GPa. The possible differences between MPPMS and DOMS were analyzed based on the plasma global model and empirical equations. The analysis revealed that the high discharge current of DOMS is primarily caused by the possibility of back-attraction ion difference between MPPMS and DOMS. The voltage oscillation in a DOMS discharge provides sufficient time for ionized ions to escape from cathode attraction. Regarding the difference in deposition rate, it should at least be the cooperative results of the target back-attraction effect and ion evacuation time difference in plasma.

A hybrid plasma model for Cr thin film deposition by deep oscillation magnetron sputtering

A time-dependent hybrid plasma model composed of a zero-dimensional global model and a two-dimensional fluid model is proposed for simulation of plasma chemistry and transportation of plasma during Cr thin film deposition by deep oscillation magnetron sputtering (DOMS). The global model deals with plasma reactions in the ionization region near the target with discharge voltage and current waveforms as inputs. The temporal plasma characteristics calculated by the global model are utilized as a boundary condition for the two-dimensional fluid model to simulate high-density plasma transportation in the diffusion region through the entire macropulse period. The full momentum equation taking inertia force into consideration is applied for ion momentum conservation in the fluid model instead of using the drift-diffusion approximation, which ensures validity of the simulation for low-pressure plasmas. The deposition flux as well as the kinetic and potential energy fluxes transferred to the growing films are calculated by the hybrid model. Microstructure evolution of the DOMS deposited Cr thin films from zone I to zone T is attributed to the growing kinetic and potential energies as the charging voltage increases according to the structure zone diagram. The deposition rate loss in DOMS is explained by the back attraction effect, sputtering yield effect, and densification of the films.

Ultrafast magnetisation dynamics in a chromium-based Prussian blue analogue

An experimental framework comprising transient transmittance and time-resolved magneto-optical measurements was used to observe ultrafast photophysics and demagnetisation dynamics in thin films of mixed-valence Cr–Cr Prussian blue analogue.

SIMULATION STUDIES OF CR DOPED CUO HETEROJUNCTION SOLAR CELL

1% and 3% Cr doped CuO thin films have been deposited on soda lime glass by spin coating method and then their structural, morphological and optical properties have been investigated by operating X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Ultraviolet-Visible Spectroscopy (UV-Vis) techniques, respectively. XRD patterns of CuO:Cr (1%) and CuO:Cr (3%) thin films demonstrate characteristics of monoclinic CuO structure with a C2/c space group. The morphology of coated film plays an important role in analyzing some optoelectronic properties. 1% Cr doped CuO thin film absorbs more photons compared to 3% Cr doped CuO in Vis and UV regions. The band gaps of 1% Cr and 3% Cr doped CuO thin films are to be 2.18 eV and 2.30 eV, respectively. The Mo/1% and 3% Cr doped CuO/n-ZnO/i-ZnO/AZO solar cell has modelled with SCAPS-1D simulation program. The photovoltaic (PV) parameters of solar cell deteriorated with some increase in the neutral defect density (N_t) value. As the shallow acceptor defect density (N_a) value is increased, J_SC is decreased, V_OC, FF and η are increased. PV performance of 1% Cr doped CuO solar cell were found to be better than that of 3% Cr doped CuO solar cell. The efficiency of 1% Cr doped CuO solar cell is increased with the use of SnO2 intermediate layer in 2 nm thickness at the heterojunction interface.

Decrypting the thermal effects on the electric field-induced material formation process on Cr thin films

Controlled electrochemical reactions on chromium (Cr) thin films have been employed to create micro- and nano-scale patterns using a scanning probe-based patterning process called electrolithography (ELG). The electrochemical reaction produces a liquid material. The ELG process, being a local anodic oxidation-based technique, is significantly affected by several factors, including various ambient conditions. In this article, we explore the effects of temperature on the said electrochemical reaction-induced liquid material formation process. Keeping other ambient conditions constant, the temperature is varied over a large range, and we observe that a 40 °C change in temperature results in a 20-time change in the radial spread of the liquid region. This observation is thereafter explained by the effect of temperature on three different parameters affecting the rate of electrochemical reaction. Thus, based on this study, we can say that temperature is one of the most crucial parameters which can be used to confine the lateral spread of the formed liquid region and thereby improve the resolution of the patterns created using the ELG technique.

The combination of electrodeposited chromium (III) and PVD as an industrial viable solution for the replacement of electrodeposited chromium (VI)

Chromium electrodeposition from hexavalent Cr (VI) aqueous solutions for Cr thin films and coatings has been vastly used for distinct purposes, due to the attractive appearance and outstanding mechanical, wear and corrosion properties of the resulting coatings. Regardless, its toxicity led to the implementation of European legislation to rescript its use, such as the European Norms Regulation on the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) and Restriction of Certain Hazardous Substances (RoHS). Thus, a replacement for Cr VI must be found, however, it would be important that the resulting films keep their characteristics. In the literature chromium electrodeposition from trivalent chromium (Cr III) aqueous solutions has been proposed and tested, however, its mechanical and optical properties are not comparable with the ones of Cr VI-based coatings and an alternative method is then required as Cr III alone does not deliver the necessary requirements. In this work, a combination of Cr III electrodeposition (ECD) in conjugation with a physical vapour deposition (PVD) multilayered coating of Cr, N, and C is explored to provide a coating capable of fulfilling the industry requirements. Subjecting the developed samples to a Neutral Salt Spray Test (ISO 9227:2027), shows that both the Cr III and Cr III + PVD coatings have similar results regarding corrosion resistance. Moreover, impedance electrochemical spectroscopy demonstrates the coating porosity as the critical point opening the door to further improvements. Aesthetically, applying the PVD layers allows for replicating the former shiny and black chromed look and expands to more different and appealing colours. Hence, this innovative alternative, based on the use of trivalent chromium by electro-deposition followed by PVD coatings, has proven potential to substitute the hexavalent chromium ECD process, while being a viable and sustainable alternative and expanding its use through different colours.

Raman Scattering of Light in Thin Films of Fe, Cr, and Ca Silicides on Silicon and Sapphire

Raman Scattering of Light in Thin Films of Fe, Cr, and Ca Silicides on Silicon and Sapphire