Optimization of large-area YBa_(2)Cu_(3)O_(7-δ)thin films by pulsed laser deposition for planar microwave devices

This paper presents high quality YBa_(2)Cu_(3)O_(7-δ)(YBCO)thin films on LaAlO_(3)substrate for microwave devices prepared by pulsed laser deposition(PLD).The double-sided YBCO films cover a large area and have been optimized for key parameters relevant to microwave device applications,such as surface morphology and surface resistance(R_(s)).This was achieved by improving the target quality and increasing the oxygen pressure during deposition,respectively.To evaluate the suitability of the YBCO films for microwave devices,a pair of microwave filters based on microstrip fabricated on films from this work and a commercial company were compared.The results show that the YBCO films in this work could completely meet the requirements for microwave devices.

Exploration of growth conditions of TaAs Weyl semimetal thin film using pulsed laser deposition

Ta As,the first experimentally discovered Weyl semimetal material,has attracted a lot of attention due to its high carrier mobility,high anisotropy,nonmagnetic properties and strong interaction with light.These make it an ideal candidate for the study of Weyl fermions and applications in quantum computation,thermoelectric devices,and photodetection.For further basic physics studies and potential applications,large-size and high-quality Ta As films are urgently needed.However,it is difficult to grow As-stoichiometry Ta As films due to the volatilization of As during the growth.To solve this problem,we attempted to grow Ta As films on different substrates using targets with different As stoichiometric ratios via pulsed laser deposition(PLD).In this work,we found that partial As ions of the Ga As substrate are likely to diffuse into the Ta As films during growth,which was preliminarily confirmed by structural characterization,surface topography and composition analysis.As a result,the As content in the Ta As film was improved and the Ta As phase was achieved.Our work presents an effective method for the fabrication of Ta As films using PLD,enabling possible use of the Weyl semimetal film for functional devices.

High temperature thermoelectric properties of highly c-axis oriented Bi_2Sr_2Co_2O_y thin films fabricated by pulsed laser deposition

High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,

Growth properties of gallium oxide on sapphire substrate by plasma-assisted pulsed laser deposition

Gallium oxide was deposited on a c-plane sapphire substrate by oxygen plasma-assisted pulsed laser deposition(PLD).An oxygen radical was generated by an inductive coupled plasma source and the effect of radio frequency(RF)power on growth rate was investigated.A film grown with plasma assistance showed 2.7 times faster growth rate.X-ray diffraction and Raman spectroscopy analysis showedβ-Ga2 O3 films grown with plasma assistance at 500℃.The roughness of the films decreased when the RF power of plasma treatment increased.Transmittance of these films was at least 80%and showed sharp absorption edge at 250 nm which was consistent with data previously reported.

Microstructure,optical,and photoluminescence properties ofβ-Ga_(2)O_(3)films prepared by pulsed laser deposition under different oxygen partial pressures

Theβ-Ga_(2)O_(3)films are prepared on polished Al_(2)O_(3)(0001)substrates by pulsed laser deposition at different oxygen partial pressures.The influence of oxygen partial pressure on crystal structure,surface morphology,thickness,optical properties,and photoluminescence properties are studied by x-ray diffraction(XRD),atomic force microscope(AFM),scanning electron microscope(SEM),spectrophotometer,and spectrofluorometer.The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure,the full width at half maximum(FWHM)and grain size increase.With the increase of oxygen pressure,the thickness of the films first increases and then decreases.The room-temperature UV-visible(UV-Vis)absorption spectra show that the bandgap of theβ-Ga_(2)O_(3)film increases from4.76 e V to 4.91 e V as oxygen pressure decreasing.Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm(~4.0 e V),360 nm(~3.44 e V),445 nm(~2.79 e V),and 467 nm(~2.66 e V),respectively.In addition,the total photoluminescence intensity decreases with oxygen pressure increasing,and it is found that the two UV bands are related to self-trapped holes(STHs)at O1 sites and between two O2-s sites,respectively,and the two blue bands originate from V_(Ga)^(2-)at Ga1 tetrahedral sites.The photoluminescence mechanism of the films is also discussed.These results will lay a foundation for investigating the Ga_(2)O_(3)film-based electronic devices.

Comprehensive Optimization of Electrical and Optical Properties for ATO Films Prepared by Pulsed Laser Deposition

Antimony doped tin oxide（ATO） thin films have been prepared by pulsed laser deposition（PLD） method.The intrinsic effect of Sb dopant,including the Sb content,transition degree between Sb（3＋） and Sb（5＋） and crystallinity on the electrical and optical properties of the ATO thin films is mainly investigated.It is suggested that the transition degree of Sb（3＋） towards Sb（5＋）（Sb（5＋）/Sb（3＋） ratio） is determined by Sb content.When the Sb content is increased to 12 at%,the Sb（5＋）/Sb（3＋） ratio reaches the highest value of 2.05,corresponding to the resistivity of 2.70×10（-3） Ω·cm.Meanwhile,the Burstein-Moss effect caused by the increase of carrier concentration is observed and the band gap of the ATO thin films is broadened to 4.0 eV when the Sb content is increased to 12 at%,corresponding to the highest average optical transmittance of 92%.Comprehensively considering the combination of electrical and optical properties,the ATO thin films deposited with Sb content of 12 at%exhibit the best properties with the highest ＂figure of merit＂ of 3.85×10（-3） Ω（-1）.Finally,an antimony selenide（Sb_2Se_3） heterojunction solar cell prototype with the ATO thin film as the anode has been prepared,and a power conversion efficiency of 0.83%has been achieved.

Preparation of Highly Textured Bi and MnBi Films by the Pulsed Laser Deposition Method

Textured Bi and MnBi/Bi thin films are prepared by the pulsed laser deposition method. The highly c-axis textured MnBi films are obtained by annealing the bilayer consisting of textured Bi and Mn films. The eoercivities of the MnBi/Bi film are 1.5 T and 2.35 T at room temperature and at 373K, respectively, showing a positive temperature coefficient. Microstructural investigations show that the textured MnBi film results from the orientated growth induced by the textured Bi under-layer.

STRUCTURE AND SURFACE STUDIES OF Mg_xZn_(1-x)O FILMS GROWN BY PULSED LASER DEPOSITION

The structural and surface properties of high-quality epitaxial cubic MgxZn1-xO films deposited by pulsed laser deposition (PLD) were studied by X-ray diffracti on and atomic force microscopy respectively. For films of about 500nm thick, sca ns over a 30μm × 30μm area revealed a surface roughness Ra of about 100nm. Th is relatively large surface roughness is primarily attributed to the particulate and outgrowth during the PLD process. A good epitaxial growth on LaAlO3 (LAO ) (100) substrates, however has been obtained for composition x = 0.9, 0.7 and 0 .5 with the heteroepitaxial relationship of (100)■∥(100)LAO (out-of-plane) and (011)■∥(010)LAO (in-plane). These structural qualities suggest that cubic Mgx Zn1-xO alloys films have good potential in a variety of optoelectronic device ap plications.

Growth of High-Quality Superconducting FeSe0.5Te0.5 Thin Films Suitable for Angle-Resolved Photoemission Spectroscopy Measurements via Pulsed Laser Deposition

High-quality superconducting FeSe0.5 Te0.5 films are epitaxiMly grown on different substrates by using the pulsed laser deposition method. By measuring the transport properties and surface morphology of films grown on single- crystal substrates of Al2O3 （0001）, SrTiO3 （001）, and MgO （001）, as well as monitoring the real-time growth process on MgO substrates with reflection high energy electron diffraction, we find the appropriate parameters for epitaxial growth of high-quality FeSe0.5 Te0.5 thin films suitable for angle-resolved photoemission spectroscopy measurements. We further report the angle-resolved photoemission spectroscopy characterization of the super- conducting films. The clearly resolved Fermi surfaces and the band structure suggest a sample quality that is as good as that of high-quality single-crystals, demonstrating that the pulsed laser deposition method can serve as a promising technique for in situ preparation and manipulation of iron-based superconducting thin films, which may bring new prosperity to angle-resolved photoemission spectroscopy research on iron-based superconductors.

Comparison of ZnO Films Grown on before- and after-vapor Transport Equilibration (VTE) LiAlO_2 Substrates by Pulsed Laser Deposition (PLD)

About φ45 mm LiAlO2 single crystal was grown by Czochralski （Cz） technique. However, the full-width at half-maximum （FWHM） value was high to 116.9 arcsec. After three vapor transport equilibration （VTE） processes, we can obtain high-quality LiAlO2 slice with the FWHM value of 44.2 arcsec. ZnO films were fabricated on as-grown slices and after-VTE ones by pulsed laser deposition （PLD）. It was found that ZnO films on the two slices have similar crystallinity, optical transmittance and optical band gap at room temperature. These results not only show that LAO substrate is suitable for ZnO growth, but also prove that the crystal quality of LAO substrate slightly affects the structural and optical properties of ZnO film.

Growth of Erbium Dihydride Films under Low Hydrogen Pressure by Pulsed Laser Deposition

Erbium dihydride thin films were prepared by pulsed laser deposition on Si（100） substrates using erbium target under different low hydrogen pressures. The properties of these films were examined by atomic force microscopy, X-ray diffractometer, transmission electron microscopy, and Fourier transform infrared spectroscopy and UV-vis spectroscopy. Surface morphology reveals the smooth surface of these films （RMS： from 0.503 to 2.849 nm）. The presence of obviously-broadened peaks for diffraction planes （111） suggests a presence of very tiny crystallites distributed along a preferred crystallographic orientation. Transmission electron microscopy investigations confirmed the formation of tiny crystallites due to the implantation of erbium ions. Due to the increase of nominal H concentration, the intensity of the broad absorbance from 190-260 nm increased.

Influence of Ambient Gas and Oxygen Pressure on Nd∶LuVO_4 Films Grown by Pulsed Laser Deposition

The （ 200 ） dominated Nd： LuVO4 films were fabricated successfully on polished SlOE under different ambient gases and different oxygen pressures. By XRD, it is shown that a film with good crystallization is deposited under oxygen and the optimal pressure is 20 Pa. The surface morphology of Nd：LuVO4 films was observed by AFM, and it is found that oxygen pressure influences the surface morphology of Nd ：LuVO4 films. The ratio of content of Nd：LuVO4 films was estimated according to the yields of Lu and V by using RBS spectra, this ratio is in good agreement with the target composition. The effective index refractive of every mode is 2.0044, 1.7098, measured by prism coupler method.

Preparation and Properties of IrO_2 Thin Films Grown by Pulsed Laser Deposition Technique

Highly conductive IrO2 thin films were prepared on Si （100） substrates by means of pulsed laser deposition technique from an iridium metal target in an oxygen ambient atmosphere. Emphasis was put on the effect of oxygen pressure and substrate temperature on the structure, morphology and resistivity of IrO2 films. It was found that the above properties were strongly dependent on the oxygen pressure and substrate temperature. At 20 Pa oxygen ambient pressure, pure polycrystalline IrO2 thin films were obtained at substrate temperature in the 300-500℃ range with the preferential growth orientation of IrO2 films changed with the substrate temperature. IrO2 films exhibited a uniform and densely packed granular morphology with an average feature size increasing with the substrate temperature. The room-temperature resistivity variations of IrO2 films correlated well with the corresponding film morphology changes. IrO2 films with the minimum resistivity of （42 ±6）μΩ·cm was obtained at 500℃.

Structural and Optical Properties of Ce^(3+), Yb^(3+) Co-doped YAG Films by Pulsed Laser Deposition

Ce3＋, Yb3＋ co-doped Y3Al5O12 films were prepared by pulse laser deposition. X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectra were used to characterize their structural and luminescent properties. Near-infrared quantum cutting from the films was observed via a cooperative energy transfer from Ce3＋ to Yb3＋ ions. The high quantum efficiency of the films implies that Ce3＋,Yb3＋ co-doped Y3A15O12 films have potential application by tuning the solar spectrum to enhance the efficiency of silicon solar cells.

Improvement of Surface Morphology of Yttrium-Stabilized Zirconia Films Deposited by Pulsed Laser Deposition on Rolling Assisted Biaxially Textured Substrate Tapes

The surface morphology of buffer layer yttrium-stabilized zirconia （YSZ） of YBa2CuaO7-σ （YBCO） high temperature superconducting films relies on a series of controllable experimental parameters. In this work, we focus on the influence of pulsed laser frequency and target crystalline type on surface morphology of YSZ films deposited by pulsed laser deposition （PLD） on rolling assisted biaxially textured substrate tapes. Usually two kinds of particles are observed in the YSZ layer： randomly distributed ones on the whole film and self-assembled ones along grain boundaries. SEM images are used to prove that particles can be partly removed when choosing dense targets of single crystalline. Lower frequency of pulsed laser also contributes to a smoother film surface. TEM images are used to view the crystalline structure of thin film. Thus we can obtain a basic understanding of how to prepare a particle-free YSZ buffer layer for YBCO in optimized conditions using PLD. The YBCO layer with nice structure and critical current density of around 5 MA/cm2 can be reached on smooth YSZ samples.

Structural and Surface Morphology Analysis of Copper Phthalocyanine Thin Film Prepared by Pulsed Laser Deposition and Thermal Evaporation Techniques

In the present paper, Copper Phthalocyanine (CuPc) thin films were deposited on glass and silicon substrate by thermal evaporation and pulsed laser deposition (PLD) methods. CuPc thin films prepared at different annealing temperatures (298, 323, 348, 373, 423 K) respectively. The structure and surface morphology of CuPc in powder and thin films forms prepared by two methods were studied using Energy dispersive X-ray (EDX), X-ray f§lt;span§gt;lorescence (XRF), X-ray§lt;/span§gt;diffraction (XRD), Atomic force microscope (AFM), and Scanning electron microscope (SEM). It showed that there was a change and enhancement in the crystallinity and surface morphology due to change in the annealing temperature (T§lt;sub§gt;a§lt;/sub§gt;). The purpose of our work is to find the optimal temperature for which the film produces best structural properties for CuPc thin film to produce organic field effect transistor. Analysis of X-ray diffraction patterns of CuPc in powder form showed that it had an α-poly-crystalline phase with monoclinic structure, with preferentially oriented (100) plane transform to §lt;i§gt;β§lt;/i§gt;-single crystalline morestable structure at different annealing temperatures.

Thermal stability of the Cr-coated zirconium alloy microstructure prepared by pulsed laser deposition

Cr-coated zirconium alloy was prepared by pulsed laser deposition(PLD)for the application of accident-tolerant fuel cladding in light water reactors.The microstructural characteristics of the Cr coating and its evolution with temperature were investigated using grazing incidence X-ray diff raction and in situ heating transmission electron microscopy(TEM).Results show that the microstructure of the laser-deposited Cr coatings consists mainly of fine and non-specific shaped nano-crystals in the inner layer and columnar crystals in the outer layer.The recrystallization of the Cr-coating layer starts at 300–400℃ to release the high strain introduced by PLD,and the grain coalescence starts at temperatures>400°C.Upon annealing,the(110)-texture gradually intensifi es because of its high reticular density and low close-packed energy.Additionally,in situ heating TEM observation shows the presence of cavities on the Cr–Zr interface,which may result from the interdiff usion and/or the transformation from amorphous to crystalline.

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Advances in energy conversion and storage technologies,such as water electrolyzers,rechargeable metal-air batteries,and fuel cells,have enabled a renewable and sustainable future.The efficiency and effectiveness of these technologies largely relies on the physicochemical properties of the functional materials used,specifically electrocatalysts.Pulsed laser deposition(PLD)is a powerful technique for the synthesis of thin film materials,offering a unique platform for understanding electrochemical reaction mechanisms and searching for low-cost and high-performance electrocatalysts.In this mini-review,we present the latest studies in which thin film materials(mainly focused on perovskite oxide thin films)via PLD have been actively utilized in the field of electrocatalysis.The fundamentals and advantages of PLD in the synthesis of thin films are discussed first.Then,emerging types of thin films associated with electrochemical applications are presented.Special emphasis is placed on material design methods to reveal the reaction mechanisms and establish the structure–performance relationships by understanding structural variations in precatalysts and surface reconstruction under reaction conditions.Finally,we discuss remaining challenges and future perspectives.

Centimeter-scale growth of two-dimensional layered high-mobility bismuth films by pulsed laser deposition

Ever since discovery of graphene,two-dimensional(2D)materials become a new tool box for information technology.Among the 2D family,ultrathin bismuth(Bi)has attracted a great deal of attention in recent years due to its unique topological insulating properties and large magnetoresistance.However,the scalable synthesis of layered Bi ultrathin films is rarely been reported,which would greatly restrict further fundamental investigation and practical device development.Here,we demonstrate the direct growth of homogeneous and centimeter-scale layered Bi films by pulsed laser deposition(PLD)technique.The as-grown Bi film exhibits high-purity phase and good crystallinity.In addition,both(111)and(110)-oriented Bi films can be synthesized by precisely controlling the processing temperature.The characterization of optical properties shows a thickness dependent band gaps(0.075-0.2 eV).Moreover,Bi thin-film-based field-effect transistors have been demonstrated,exhibiting a large carrier mobility of 220 cm2 V−1 s−1.Our work suggests that the PLD-grown Bi films would hold the potential to develop spintronic applications,electronic and optoelectronic devices used for information science and technology.

Effect of interface on mid-infrared photothermal response of MoS2 thin film grown by pulsed laser deposition

This study reports on the mid-infrared （mid-IR） photothermal response of multilayer MoS2 thin films grown on crystalline （p-type silicon and c-axis- oriented single crystal sapphire） and amorphous （Si/SiO2 and Si/SiN） substrates by pulsed laser deposition （PLD）. The photothermal response of the MoS2 films is measured as the changes in the resistance of the MoS2 films when irradiated with a mid-IR （7 to 8.2 μm） source. We show that enhancing the temperature coefficient of resistance （TCR） of the MoS2 thin films is possible by controlling the film-substrate interface through a proper choice of substrate and growth conditions. The thin films grown by PLD are characterized using X-ray diffraction, Raman, atomic force microscopy, X-ray photoelectron microscopy, and transmission electron microscopy. The high-resolution transmission electron microscopy （HRTEM） images show that the MoS2 films grow on sapphire substrates in a layer-by-layer manner with misfit dislocations. The layer growth morphology is disrupted when the films are grown on substrates with a diamond cubic structure （e.g., silicon） because of twin growth formation. The growth morphology on amorphous substrates, such as Si/SiO2 or Si/SiN, is very different. The PLD-grown MoS2 films on silicon show higher TCR （-2.9% K^-1 at 296 K）, higher mid-IR sensitivity （△R/R = 5.2%）, and higher responsivity （8.7 V·W^-1） compared to both the PLD-grown films on other substrates and the mechanically exfoliated MoS2 flakes transferred to different substrates.