Room Temperature Pulsed Laser Deposition Research Articles

Resistive switching suppression in metal/Nb:SrTiO3 Schottky contacts prepared by room-temperature pulsed laser deposition

Deepening the understanding of interface-type resistive switching (RS) in metal/oxide heterojunctions is a key step for the development of high-performance memristors and Schottky rectifiers. In this study, we address the role of metallization technique by fabricating prototypical metal/Nb-doped SrTiO3 (M/NSTO) Schottky contacts via pulsed laser deposition (PLD). Ultrathin Pt and Au electrodes are deposited by PLD onto single-crystal (001)-terminated NSTO substrates and interfacial transport is characterized by conventional macroscale methods and nanoscale Ballistic Electron Emission Microscopy. We show that PLD metallization gives Schottky contacts with highly reversible current-voltage characteristics under cyclic polarization. Room-temperature (RT) transport is governed by thermionic emission with Schottky barrier height ϕB(Pt/NSTO)∼0.71−0.75eV , ϕB(Au/NSTO)∼0.70−0.83eV and ideality factors as small as n(Pt/NSTO)∼1.1 and n(Au/NSTO)∼1.6 . RS remains almost completely suppressed upon imposing broad variations of the Nb doping and of the external stimuli (polarization bias, working temperature, ambient air exposure). At the nanoscale, we find that both systems display high spatial homogeneity of ϕB ( ⩽50meV ), which is only partially affected by the NSTO mixed termination ( |ϕB(M/SrO)−ϕB(M/TiO2)|<35meV ). Experimental evidences and theoretical arguments—based on a metal-insulator-semiconductor description of the M/NSTO—indicate that the PLD metallization mitigates interfacial layer effects responsible for RS. This occurs thanks to the reduction of the interfacial layer thickness and to the creation of an effective barrier against the permeation of ambient gas species affecting charge trapping and redox reactions. This description allows to rationalize interfacial aging effects, observed upon several-months-exposure to ambient air, in terms of a slow interfacial re-oxidation. Our work contributes to the fundamental understanding of interface-type RS and demonstrates that RT PLD offers a viable platform for the realization of robust, RS-free NSTO-based Schottky contacts.

High-quality VO2 films synthesized on polymer substrates using room-temperature pulsed laser deposition and annealing

With the growing trend towards portable and adaptable devices in various fields, the demand for flexible electronics and coatings utilizing phase transition materials like VO2 as a functional layer is rising. However, depositing high-quality crystalline VO2 films directly onto polymer substrates remains challenging due to the thermosensitivity of such materials being barely compatible with usual VO2 deposition methods. In this study, we present a simple method for directly growing VO2 on Kapton substrates. VOx films were first deposited onto the Kapton substrate at room temperature using pulsed laser deposition and subsequently annealed in an oxygen atmosphere at 390 °C. The electrical and optical properties of the VO2/Kapton samples with different film thicknesses were investigated. The 200 nm-thick vanadium dioxide films exhibit the best resistivity contrast with 3.1 orders of magnitude (OOM), while the 50 nm-thick films show the best transmittance change of 54 % at 2500 nm. The switching performances are comparable or even superior to those achieved previously using more complicated synthesis processes such as film transfer, introduction of buffer layers, and ink injection. Additionally, by coupling W elemental doping and thin film strain, we successfully tuned the VO2 transition temperature to room temperature with a dopant concentration of only 1.1 at.% while maintaining a high electrical contrast (2 OOM). The impressive electrical and optical transition performance of the VO2/Kapton samples, combined with their tunable transition temperature, makes them promising candidates for flexible electronic devices and thermochromic smart coatings.

Wafer-Scale Synthesis of 2D Materials by an Amorphous Phase-Mediated Crystallization Approach.

The interest in the wafer-scale growth of two-dimensional (2D) materials, including transition metal dichalcogenides (TMDCs), has been rising for transitioning from lab-scale devices to commercial-scale systems. Among various synthesis techniques, physical vapor deposition, such as pulsed laser deposition (PLD), has shown promise for the wafer-scale growth of 2D materials. However, due to the high volatility of chalcogen atoms (e.g., S and Se), films deposited by PLD usually suffer from a lack of stoichiometry and chalcogen deficiency. To mitigate this issue, excess chalcogen is necessary during the deposition, which results in problems like uniformity or not being repeatable. This study demonstrates a condensed-phase or amorphous phase-mediated crystallization (APMC) approach for the wafer-scale synthesis of 2D materials. This method uses a room-temperature PLD process for the deposition and formation of amorphous precursors with controlled thicknesses, followed by a post-deposition crystallization process to convert the amorphous materials to crystalline structures. This approach maintains the stoichiometry of the deposited materials throughout the deposition and crystallization process and enables the large-scale synthesis of crystalline 2D materials (e.g., MoS2 and WSe2) on Si/SiO2 substrates, which is critical for future wafer-scale electronics. We show that the thickness of the layers can be digitally controlled by the number of laser pulses during the PLD phase. Optical spectroscopy is used to monitor the crystallization dynamics of amorphous layers as a function of annealing temperature. The crystalline quality, domain sizes, and the number of layers were explored using nanoscale and atomistic characterization (e.g., AFM, STEM, and EDS) along with electrical characterization to explore process-structure-performance relationships. This growth technique is a promising method that could potentially be adopted in conventional semiconductor industries for wafer-scale manufacturing of next-generation electronic and optoelectronic devices.

Crystallinity improvement of room-temperature PLD-deposited ZnO thin films on cyclo-olefin polymer substrates subject to surface-pretreatment with vacuum-UV-light irradiation

The effect of the surface-pretreatment of cyclo-olefin polymer (COP) substrates with vacuum-ultraviolet (VUV) light irradiation on the crystal growth of ZnO thin films deposited by room-temperature pulsed laser deposition (PLD) was investigated for development of flexible optical devices. 172-nm-excimer light irradiation with durations of 60 to 600 s in air was found to make the COP surface more hydrophilic and smooth. It was verified from measurements of X-ray diffraction, atomic force microscope and high-resolution transmission electron microscope that the ZnO thin films grown on the VUV-light-pretreated COP substrates exhibited enhanced (0001) orientation growth and increased crystallinity compared with the samples grown on substrates not subject to the pretreatment; the samples on the pretreated substrates also showed a smooth surface and atomically sharp interface between the thin film and the substrate. The electrical resistivity of the ZnO thin film grown on the VUV-light-pretreated COP substrate was estimated to be 2.3 × 10−3 Ωcm, which was 40% lower than that of the film grown on the untreated substrate.

Thermal neutron conversion by high purity 10B-enriched layers: PLD-growth, thickness-dependence and neutron-detection performances

Neutron applications and detection are of paramount importance in industry, medicine, scientific research, homeland security, production of extreme UV optics and so on. Neutron detection requires a converter element that, as a result of its interaction with neutrons, produces reaction products (mainly charged particles) whose detection can be correlated with the neutron flux. Reduced availability and increased cost of the most used converter element, 3He, have triggered research efforts for alternative materials, proper deposition methods and new detector architectures. 10B converter is a valid alternative to 3He thanks to its high thermal neutron cross section and relatively high Q value. In this paper we report on the room temperature Pulsed Laser Deposition (PLD) of high quality and uniform 10B films with the expected density, different thickness values (0.5, 1.0, 1.2, 1.5 and 2.0 μm) and uniform thickness over a circular area of about 30 mm in diameter. Additionally, they are adherent to the substrate with a negligible presence of contaminants. The conversion properties of such 10B coatings coupled to a Si solid state detector are studied upon exposure to a neutron flux from an Am-Be neutron source (2.2·106 n/s). The experimental results, compared with spectra simulated by using a GEANT4 code, present a good agreement and efficiencies of the order of a few percent.

Growth of Al-doped ZnO nanostructures in low pressure background gas by pulsed laser deposition

In this work, the deposition of nanostructures by room temperature pulsed laser deposition (PLD) in low pressure (2.6 Pa) O2, N2, He, and Ar at different substrate positions are studied. The substrates are placed at the normal on-axis/center position; and off-axis i.e. 4.5 cm above and below the center position. Optical emission spectra and ion velocity are measured by using spectrometer and ion probe. The overall intensity of optical emission is in the order of Ar > O2/N2 > He while the ion velocity is in the reverse order. The inverse relation of optical emission and ion velocity suggest that collisions of the ablated specie possibly result in strong emission and impede the ion velocity at the same time. Amorphous films are obtained for the substrates placed at on-axis/center in all the background gases and at the bottom position for O2. However, crystalline ZnO and Zn nanostructures are deposited at the bottom position in N2, He, and Ar. Larger structures are deposited in Ar and the presence of nanorods are detected by TEM. The results further suggest that in N2, He or Ar, the ablated plasma plume is spatially and thermally confined; governed by the properties of the gas. Nucleation of nanostructures occurred in the plasma plume even at low background pressure and deposited on the substrates that are placed at the bottom position. Between the two inert gases, Ar with higher atomic mass and lower thermal conductivity results in high collisions and thermal confinement that leads to some large structure as compared to those obtained in He. In addition, in the presence of N2, He or Ar, Zn crystallites are also detected, which can act as catalyst for nanostructure formation.

Neo-heterojunction based on the kesterite copper chalcogenide semiconductor with magnetic iron-cation partial-substitution: In-situ room-temperature pulsed laser deposition and optoelectronic properties

For improving optoelectronic properties of copper chalcogenide semiconductors such as Cu2ZnSnS4 (CZTS), we explore to optimize CZTS itself and construct heterostructures on the perspective of semiconductor device design. Specifically, in order to suppress widely existed CuZn and ZnCu antisite defects of pure CZTS, we synthesize 25%-Fe-doped CZTS (CZFTS) thin films through partial substitution of magnetic iron for zinc; we further integrate electron acceptor Bi2S3 to CZFTS and constitute CZFTS/Bi2S3 heterostructure. Our newly-developed in-situ room-temperature pulsed laser deposition (PLD) technique is adopted to prepare the bilayer sulfide films without post-sulfurization process, effectively optimizing CZFTS-Bi2S3 interfaces. Chronoamperometric measurements demonstrate that CZFTS/Bi2S3 heterojunction has at least one order-of-magnitude improvement in photoelectric response speed within visible light (Vis) region compared to single CZFTS film, and responding time is decreased to a few milliseconds. Hereby, the synergistically combining partial cation substitution and in-situ PLD technique is promising to develop the Vis-active CZTS-based thin-film photodetectors in an effective and efficient way as well as to economically produce such analogous thin-film photoelectric devices based on polynary chalcogenide.

Correlating Crystallization-Induced Structural and Electrical Evolutions in SrTi0.65Fe0.35O3-X Thin Films

Rapid oxygen exchange kinetics and fast ionic and electronic transport are central to the performance of materials in solid-state electrochemical devices, such as metal-air batteries, solid oxide fuel/electrolysis cells, and gas sensors [1]. When fabricated at high temperatures, these materials are plagued by surface segregation of large cations, which leads to sluggish oxygen exchange [2]. When further operated at high temperatures, ongoing surface degradation can occur, while operation at low temperatures yields higher electrical resistances and even slower oxygen surface exchange kinetics due to their thermally-activated nature. By contrast, recent work in our group has demonstrated a low-thermal-budget route to fabricate SrTi0.65Fe0.35O3-x (STF35) thin films with enhanced low-temperature oxygen exchange kinetics by crystallizing amorphous-grown STF35 thin films, thereby maintaining a low Sr surface concentration [3,4]. While this result is promising, the crystallization-induced structural evolution and its influence on the charge transport behavior have yet to be studied.In this work, amorphous STF35 thin films grown by room temperature pulsed laser deposition (PLD) were used to study the relationship between structure and conductivity during crystallization of a mixed conductor. The degree of crystallinity and local ion environment were evaluated by X-ray diffraction (XRD) and synchrotron X-ray absorption spectroscopy (XAS). In situ AC impedance spectroscopy was used to monitor the conductivity of the film during crystallization over a 400 °C isothermal hold in a controlled gas environment. The dependence of the conductivity on the volume percent crystalline showed two distinct behaviors: a small, fast increase in conductivity after a short time at temperature and a larger, percolation-type increase later in the anneal. The percolation behavior suggests a microstructural influence on the transport behavior. From the XAS results, we observed an increase in the oxidation number of Fe within the first 10 minutes of the anneal, indicating rapid oxidation. Additionally, there was an increase in symmetry and coordination number in the Fe coordination unit over the first 30 minutes of the anneal, which is correlated to an increase in the orbital overlap of the O 2p and Fe 3d orbitals and thus the hole mobility. Combined with the conductivity and XRD results, the difference in annealing-time dependence of the Fe oxidation state and Fe coordination unit symmetry enable us to separate the relative contributions of changing orbital overlap, hole concentration, and microstructure to the evolving charge transport behavior.[1] Hong, W.T., Risch, M., Stoerzinger, K.A., Grimaud, A., Suntivich, J. and Shao-Horn, Y., 2015. Energy & Environmental Science, 8(5), pp.1404-1427.[2] Perry, N.H. and Ishihara, T., 2016. Materials, 9(10), p.858.[3] Chen, T., Harrington, G.F., Sasaki, K. and Perry, N.H., 2017. Journal of Materials Chemistry A, 5(44), pp.23006-23019.[4] Chen, T., Harrington, G., Masood, J., Sasaki, K. and Perry, N.H., 2019. ACS applied materials & interfaces.

Low-Temperature Laser Synthesis of Thin Electrochromic WO3 Films

Amorphous dielectric WO3 films with a surface roughness from 4 to 5 nm have been grown by room-temperature pulsed laser deposition on quartz and c-sapphire substrates using metallic targets. We have examined the effect of the nature of the substrates and the oxygen pressure during the growth process on the transmission spectrum of the WO3 films in the range from 400 to 2000 nm. The parameters of the films have been shown to depend on the oxygen pressure during the growth process. Raising the oxygen pressure from 20 to 60 mTorr during the film growth process increases the transmission of the WO3 films from 40 to 75% in the visible and UV spectral regions and from 10 to 70% in the IR. With increasing oxygen pressure during film growth, the band gap of the WO3 films increases from 3.01 to 3.34 eV in the case of sapphire substrates and from 2.95 to 3.42 eV in the case of quartz substrates, being only slightly dependent on the nature of the substrate. Using a WO3 film grown at room temperature, we have fabricated the first thin-film liquid-electrolyte electrochromic cell. Its transmission in the spectral range from 300 to 900 nm drops by 30% at an applied voltage of 2.5 V, with a coloration time on the order of 2 min.

Pronounced effects of oxygen growth pressure on structure and properties of ZnO and AZO films laser deposited on Zeonor polymer

We report the pronounced effects of oxygen growth pressure (0.13Pa–40Pa) on the surface morphology, hydrophobicity, structural, optical and electrical properties of ZnO and aluminium-doped ZnO (AZO) thin films deposited by room temperature pulsed-laser deposition on the low water-absorbing polymer Zeonor. Significant changes were observed for oxygen growth pressures below ~10Pa. In this pressure range, the morphology changed from nanocrystalline to that of a continuous film with a shift of the growth orientation of the crystalline fraction of the deposit from c-plane to m-plane. The appearance of valley-shaped surface cracks caused a significant increase of rms surface roughness, reduced hydrophobicity and shift to hydrophilicity at 0.13Pa. The visible optical transmittance of the film reduced from an average of 90% to 65% and the orange/red deep level emission was quenched. The electrical properties showed decreasing resistivities (105Ωcm to 10−3Ωcm) and Hall mobilities (35cm2/V-s to 3cm2/V-s) and increasing carrier concentrations (1011cm−3 to 1021cm−3). These significant changes of the films physical characteristics were related to the morphological and structural changes induced by the change of oxygen growth pressure. The observed effects are interesting for applications in flexible optoelectronics and briefly discussed in this context.

Thermoelastic-tunable magnetic response of BiFeO3thin film on colloidal photonic crystal substrate fabricated by pulsed laser deposition

Investigation of the thermoelastic-tunable magnetic response of polycrystalline bismuth ferrite thin film is herein reported. The polycrystalline bismuth ferrite thin films were grown by room-temperature pulsed laser deposition on the designed polymer colloidal photonic crystal substrates. The evolution of these films was assessed by X-ray diffraction testing and scanning electron microscopy images. The thermal-dependent magnetic measurements and magneto-optical properties were also investigated as a function of deposition substrate and target–substrate distances via the Faraday rotation method. Due to the large anisotropic thermal deformation of the polymer colloidal interface, the huge rotation downshift was observed versus a slight thermal change. Furthermore, we found that this returnable reduction had the same behavior during the heating and cooling processes. This reversible thermal property of the polymer colloidal crystal in combination with the magnetic response of the multiferroic compounds can possibly lead to innovations in sensors and switches based on thermomagneto-optical coupling and facilitate the nanoscale thermal characterization.

Influence of the Cation Ratio on Optical and Electrical Properties of Amorphous Zinc-Tin-Oxide Thin Films Grown by Pulsed Laser Deposition.

Continuous composition spread (CCS) methods allow fast and economic exploration of composition dependent properties of multielement compounds. Here, a CCS method was applied for room temperature pulsed laser deposition (PLD) of amorphous zinc-tin-oxide to gain detailed insight into the influence of the zinc-to-tin cation ratio on optical and electrical properties of this ternary compound. Our CCS approach for a large-area offset PLD process utilizes a segmented target and thus makes target exchange or movable masks in the PLD chamber obsolete. Cation concentrations of 0.08-0.82 Zn/(Zn + Sn) were achieved across single 50 × 50 mm(2) glass substrates. The electrical conductivity increases for increasing tin content, and the absorption edge shifts to lower energies. The free carrier concentration can be tuned from 10(20) to 10(16) cm(-3) by variation of the cation ratio from 0.1 to 0.5 Zn/(Zn + Sn).

Tuning electrical properties of hierarchically assembled Al-doped ZnO nanoforests by room temperature Pulsed Laser Deposition

Large surface area, 3D structured transparent electrodes with effective light management capability may represent a key component in the development of new generation optoelectronic and energy harvesting devices. We present an approach to obtain forest-like nanoporous/hierarchical Al-doped ZnO conducting layers with tunable transparency and light scattering properties, by means of room temperature Pulsed Laser Deposition in a mixed Ar:O2 atmosphere. The composition of the background atmosphere during deposition can be varied to modify stoichiometry-related defects, and therefore achieve control of electrical and optical properties, while the total background pressure controls the material morphology at the nano- and mesoscale and thus the light scattering properties. This approach allows tuning electrical resistivity over a very wide range (10−1−106Ωcm), both in the in-plane and cross-plane directions. Optical transparency and haze can also be tuned by varying the stoichiometry and thickness of the nano-forests.

Highly transparent and reproducible nanocrystalline ZnO and AZO thin films grown by room temperature pulsed-laser deposition on flexible Zeonor plastic substrates

Zeonor plastics are highly versatile due to exceptional optical and mechanical properties which make them the choice material in many novel applications. For potential use in flexible transparent optoelectronic applications, we have investigated Zeonor plastics as flexible substrates for the deposition of highly transparent ZnO and AZO thin films. Films were prepared by pulsed laser deposition at room temperature in oxygen ambient pressures of 75, 150 and 300 mTorr. The growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of as-grown films with thicknesses ∼65–420 nm were recorded for the three oxygen pressures. The growth rates were found to be highly linear both as a function of film thickness and oxygen pressure, indicating high reproducibility. All the films were optically smooth, hydrophobic and nanostructured with lateral grain shapes of ∼150 nm wide. This was found compatible with the deposition of condensed nanoclusters, formed in the ablation plume, on a cold and amorphous substrate. Films were nanocrystalline (wurtzite structure), c-axis oriented, with average crystallite size ∼22 nm for ZnO and ∼16 nm for AZO. In-plane compressive stress values of 2–3 GPa for ZnO films and 0.5 GPa for AZO films were found. Films also displayed high transmission greater than 95% in some cases, in the 400–800 nm wavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to n-type conductive was observed for the films, with resistivity ∼103 Ω cm and Hall mobility in 4–14 cm2 V−1 s−1 range, showing marked dependences on film thickness and oxygen pressure. Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested.

Tuning of Electrical and Optical Properties of Highly Conducting and Transparent Ta-Doped TiO2Polycrystalline Films

We present a detailed study on polycrystalline transparent conducting Ta-doped TiO2 films, obtained by room-temperature pulsed laser deposition followed by an annealing treatment at 550 °C in vacuum. The effects of Ta as a dopant element and of different synthesis conditions are explored to assess the relationship between material structure and functional properties, that is, electrical conductivity and optical transparency. We show that for the doped samples, it is possible to achieve low resistivity (of the order of 5 × 10–4 Ω cm) coupled with transmittance values exceeding 80% in the visible range, showing the potential of polycrystalline Ta:TiO2 for application as a transparent electrode in novel photovoltaic devices. The presence of trends in the structural (crystalline domain size, anatase cell parameters), electrical (resistivity, charge carrier density, and mobility), and optical (transmittance, optical band gap, effective mass) properties as a function of the oxygen background pressure and laser ...

Growth of c-axis-oriented superconducting KFe₂As₂ thin films.

KFe2As2, an iron-based superconductor, is expected to exhibit large spin Hall conductivity, and fabrication of high-quality thin films is requisite for evaluation of this effect and application to spintronics devices. Thin-film growth of KFe2As2 is difficult because of two intrinsic properties; its extremely hygroscopic nature and the high vapor pressure of potassium. We solved these issues by combining room-temperature pulsed laser deposition using K-rich KFe2As2 targets with thermal crystallization in KFe2As2 powder after encapsulation in an evacuated silica-glass tube with all of the processes conducted in a vacuum chamber and a dry Ar atmosphere in a glovebox. The optimized KFe2As2 films on (La,Sr)(Al,Ta)O3 single-crystal substrates were obtained by crystallization at 700 °C, and they were strongly c-axis oriented. The electrical measurements were performed with thin films protected by grease passivation to block reaction with the atmosphere. The KFe2As2 films exhibited a superconductivity transition at 3.7 K.

Room temperature deposition of alumina-doped zinc oxide on flexible substrates by direct pulsed laser recrystallization

In this study, a method combining room temperature pulsed laser deposition (PLD) and direct pulsed laser recrystallization (DPLR) is introduced to deposit transparent conductive oxide (TCO) layer on low melting point flexible substrates. Alumina-doped zinc oxide (AZO), as one of the most promising TCO candidates, has now been widely used in solar cells. However, to achieve optimal, electrical, and optical properties of AZO on low melting point, flexible substrate is challenging. DPLR technique is a scalable, economic, and fast process to remove crystal defects and generate recrystallization at room temperature. It features selective processing by only heating up the TCO thin film and preserve the underlying substrate at low temperature. In this study, AZO thin film is pre-deposited by PLD on flexible and rigid substrates. DPLR is then introduced to achieve a uniform TCO layer on these substrates, i.e., commercialized Kapton polyimide film, micron-thick Al-foil, and sold lime glass (SLG). Both finite element analysis simulation and designed experiments are carried out to demonstrate that DPLR is promising in manufacturing high quality AZO layers without any damage to the underlying flexible substrates. The hall mobility of AZO after DPLR on Kapton and SLG reached 198 cm2/v · s and 398 cm2/v · s respectively, while the carrier concentrations are reduced to 2.68 × 1018 and 4.3 × 1019/cm−2, respectively. These characteristics are exactly what an ideal TCO layer should carry: high conductivity and high transmission. The property changes are due to the reduction of defect density after DPLR.

Tailoring the photoluminescence of PbS-nanoparticles layers deposited by means of the pulsed laser ablation technique

In this article, we report on the room-temperature pulsed laser deposition (PLD) of lead sulfide (PbS) nanoparticles (NPs) layers onto various substrates. It is particularly shown that the average size of PbS NPs can be controlled by varying the number of laser ablation pulses. The pulsed laser deposited PbS NPs are found to be of high-crystalline quality and their photoluminescence (PL) to blue shift significantly from 1420 to 880 nm, as their average diameter is decreased from 8.5 to 2.5 nm, thereby confirming the quantum size effect. The latitude of our PLD process is shown to permit the achievement of multilayered PbS-NPs structures of which the overall PL emission spectrum can be tailored through the appropriate stack of individual PbS-NPs layers.

Room temperature pulsed laser deposition of Si x C thin films in different compositions

Amorphous silicon–carbon alloy films in different compositions were prepared by pulsed laser deposition from two-component targets containing pure silicon and carbon parts. The silicon–carbon ratio in the films was varied by adjusting the number of laser shots on the constituent silicon and carbon targets. The composition, optical properties, thickness, and bonding structure of the films were determined by backscattering spectrometry, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy, respectively. Backscattering spectrometry data were used to determine the deposition rate of silicon and carbon. This enabled the calculation of the number of the shots onto each target to reach a predefined composition. As the film composition changed from carbon to silicon, it was shown that the microscopic and macroscopic properties of the films also changed from a diamond-like carbon phase to an amorphous silicon phase via graphite- and silicon-carbide-like composite.

Violet luminescence from ZnO nanorods grown by room temperature pulsed laser deposition

ZnO thin films were deposited at room temperature by pulsed laser deposition (PLD) varying the oxygen pressure. Morphological analysis using scanning electron microscope (SEM) and atomic force microscopy (AFM) demonstrated the formation of ZnO nanorods at a particular oxygen pressure. Room temperature violet luminescence was observed from these ZnO nanorods and temperature dependence of luminescence was studied. Influence of oxygen pressure on the growth of ZnO thin films by PLD was studied using the X-ray photoelectron spectroscopy of both post ablated targets and deposited films. The ZnO films were crystalline and the formation of crystalline phase is found to follow a pressure–temperature ( P– T) scaling with increase of temperature.