Magnetic Behavior of Surface Nanostructured 50-nm Nickel Thin Films

Thermally evaporated 50-nm nickel thin films coated on borosilicate glass substrates were nanostructured by excimer laser (0.5 J/cm², single shot), DC electric field (up to 2 kV/cm) and trench-template assisted technique. Nanoparticle arrays (anisotropic growth features) have been observed to form in the direction of electric field for DC electric field treatment case and ruptured thin film (isotropic growth features) growth for excimer laser treatment case. For trench-template assisted technique; nanowires (70–150 nm diameters) have grown along the length of trench template. Coercive field and saturation magnetization are observed to be strongly dependent on nanostructuring techniques.     

Structural and optical studies on sol–gel derived ZnO thin films by excimer laser annealing

High-quality polycrystalline ZnO thin films were deposited onto alkali-free glasses at a temperature of 300°C in air ambience by combining sol–gel spin coating and KrF excimer laser annealing. The effects of laser irradiation energy density on the crystallization, microstructure, surface morphology, and optical transmittance of as-prepared ZnO thin films were investigated and compared to the results of thermally annealed ZnO thin films. The crystallinity level and average crystallite size of laser annealed ZnO thin films increased as laser energy density increased. The crystallinity levels and average crystallite size of excimer laser annealed (ELA) thin films were greater than those of the thermally annealed (TA) thin films. However, laser annealed thin films had abnormal grain growth when irradiation energy density was 175 mJ/cm². Experimental results indicated that the optimum irradiation energy density for excimer laser annealing of ZnO sol–gel films was 150 mJ/cm². The ELA 150 thin films had a dense microstructure, an RMS roughness value of 5.30 nm, and an optical band gap of 3.38 eV, close to the band gap of a ZnO crystal (3.4 eV).     

Optical and microstructural properties of diamond-like carbon films grown by pulsed laser deposition

Diamond-like carbon films have been fabricated using 308 nm excimer laser ablation in vacuum followed by deposition at temperatures between 77 K and 573 K. Optical band gap energies are obtained from UV/optical spectroscopy. Raman spectra and X-ray photoelectron spectra (XPS) show that the sp³/(sp² + sp³) ratio in these films is in excess of 0.7 in films deposited at 77 K and 300 K. This ratio decreases to 0.2 in films deposited at 573 K. It is found that films deposited at cryogenic temperatures consist of a matrix structure assembled from embedded nanometer clusters, while films deposited at 300 K or higher temperature are amorphous and atomically flat. Microstructural features in cryogenic films are discussed in relation to the mechanism of deposition and possible phase transitions during assembly of these films.     

Excimer laser darkening of ETFE polymer films

Darkening of ethylene–tetrafluorethylene (ETFE) films caused by exposure to xenon chloride excimer laser radiation at 308 nm was studied. Darkening was determined to result from a rapid, local heating of the film. The laser-induced heating caused elimination of hydrogen fluoride from the film, leaving a noncrystalline graphitic backbone. A threshold laser fluence for darkening of (205 ± 25) mJ/cm² was observed. At laser fluences above this threshold the rate of darkening of the ETFE films increased linearly with laser fluence. The rate of darkening was found to decrease as the extent of crosslinking in the polymer sample increased. Observations suggest that low concentrations of monomers in the film might affect the darkening rate.     

Preparation and characterization of Al-doped ZnO piezoelectric thin films grown by pulsed laser deposition

Undoped and Al-doped ZnO (AZO) thin films (Al: 3, 5 at%) using a series of high quality ceramic targets have been deposited at 450 ºC onto glass substrates using PLD method. The used source was a KrF excimer laser (248 nm, 25 ns, 2 J/cm²). The study of the obtained thin films has been accomplished using X-ray diffraction (XRD), M-lines spectroscopy and Rutherford backscattering spectroscopy (RBS). XRD patterns have shown that the films crystallize in a hexagonal wurtzite type structure with a highly c-axis preferred (002) orientation, and the grain sizes decrease from 37 to 25 nm with increasing Al doping. The optical waveguiding properties of the films were characterized by means of the prism-coupling method. The distinct M-lines of the guided transverse magnetic (TM) and transverse electric (TE) modes of the ZnO films waveguide have been observed. The M-lines device has allowed determination of the accurate values of refractive index and thickness of the studied ZnO and AZO thin films. An evaluation of experimental uncertainty and calculation of the precision of the refractive index and thickness were developed on ZnO films. The RBS results agree with XRD and m-lines spectroscopy measurements.     

Characterization of low-temperature solution-processed indium–zinc oxide semiconductor thin films by KrF excimer laser annealing

We have employed KrF excimer laser annealing (ELA) treatment on sol–gel derived indium–zinc oxide (IZO) precursor films to develop a method of low thermal-budget processing. As-coated IZO sol–gel film was dried at 150 °C and then annealed using KrF excimer laser irradiation under ambient air. The laser irradiation energy density was adjusted to 150, 250, 350, and 450 mJ/cm² to investigate the effects of laser irradiation energy density on the microstructure, surface morphology, optical transmittance, and electrical properties of laser annealed IZO thin films. Results of GIXRD and TEM-SAED indicated that the ELA IZO thin films had an amorphous phase structure. The surface characteristics and electrical properties of laser annealed IZO thin films were significantly affected by the laser irradiation energy density. It was found that the dried IZO sol–gel films irradiated with a laser energy density of 350 mJ/cm² exhibited the flattest surface, the highest average optical transmittance in the visible region, and the best electrical properties among all ELA samples.     

Excimer laser reduction and patterning of graphite oxide

A successful approach and the operational parameters necessary for reduction of graphite oxide (GO) to multilayer graphene using 248 nm excimer laser irradiation in both vacuum and ultrahigh purity N₂ background environments is described. The utility of excimer laser reduction is demonstrated by production of simple line and logo patterns using standard microscale lithographic patterning strategies. Multilayer graphene formation is confirmed with Raman and X-ray photoelectron spectroscopies, and the morphology of the processed GO sample is evaluated with scanning electron microscopy. Four-point probe measurements of the excimer laser reduced GO indicate typical sheet resistances of ∼100–500 Ω/sq, which is a significant improvement over other values reported in the literature for other laser-based GO reduction methods.     

Laser-transfer processing of functional ceramic films

Pulsed excimer laser irradiation through a UV-transparent fabrication substrate has been successfully employed to separate PZT thick films from their sapphire host substrates. Films of 20 μm in thickness were prepared by a hybrid particle sol–gel synthesis route. The microstructure, morphology and ferroelectric properties of the thick films after laser-transfer have been examined. Films were irradiated with a 248 nm, 15 ns pulse, and transferred to a platinised silicon substrate (Pt/Ti/SiO₂/Si). A laser fluence of 250 mJ/cm² was sufficient to delaminate the original PZT/sapphire interface. The pulsed energy density used here is lower than reported by other groups utilising a laser-transfer process for PZT. This is believed to be due to higher levels of porosity at the film/substrate interface in this study.     

Arylazophosphonate containing polymers designed for XeCl excimer laser ablation

Applying the N‐P coupling technique, fifteen new poly(arylazophosphonate)s were synthesized by interfacial polycondensation from bifunctional diazonium salts and bifunctional phosphoric diesters. Because of their excellent film forming properties and absorption behaviour poly(arylazophosphonate)s are suitable materials for laser ablation experiments with XeCl excimer lasers (308 nm). A variety of ablated structures have been generated by irradiation of the polymer films with a commercially available pulsed XeCl excimer laser. Macro experiments indicate remarkable structures with sharp edges, clear contours, and flat bottoms. Moreover, various patterns with μm dimensions were generated by micro experiments and were characterized by means of scanning electron microscopy (SEM). The resolution of these structures indicate that poly(arylazophosphonate)s are suitable materials for applications in microtechnology.     

Effect of XeF laser treatment on structure of nanocrystalline diamond films

Nanocrystalline diamond (NCD) films were deposited on Si substrates by microwave plasma-enhanced chemical vapor deposition (MPECVD) using methane/hydrogen/oxygen (30/169/0.2 sccm) as process gases. Subsequently a thin (0.33 μm) and a thick (1.01 μm) NCD films were irradiated with XeF excimer laser (λ = 351 nm) with 300 and 600 mJ cm^? 2 of energy densities in air. The NCD films became rougher after laser irradiations. Fraction of graphitic clusters decreased but oxygen content increased in the thin NCD film after laser irradiation. Opposite phenomena were observed for the thick NCD films. Effect of laser irradiation to oxygenation and graphitization of NCD films was correlated with structural properties of free surface and grain boundaries of the thin and thick NCD films.     

Tetrahydropyranyl- and furanyl-protected polyhydroxystyrene in chemical amplification systems

Tetrahydropyranyl- (THP) and furanyl- (THF) protected polyhydroxystyrene (PHS) polymers have been investigated for their potential use in conjunction with onium salt acid precursors to yield high-sensitivity resist systems. The synthesized polymers have high transmittance at 248 nm (the wavelength used in next-generation excimer laser, KrF exposure tools). At 248 nm the transmittance for a 1-μm thick film is ～ 80% (Abs = 0.097 μm^?1). The acid sensitivity of the acetal functionality at room temperature is high, requiring careful handling of all materials to prevent any premature deprotection of the hydroxy group. The highest lithographic sensitivities obtained so far with a system consisting of poly(p-tetrahydropyranyl-oxy-styrene) base resin and 1 mol % of bis (p-tert-butyl phenyl) iodinium triflate (TBIT) was ～ 2 mJ / cm². High-resolution line and space patterns (0.35 μm) were obtained with a system comprising PHS-p-THP and an acid precursor, using an excimer laser step and repeat exposure at 248 nm.     

Pulsed laser deposition of glass-like cluster assembled carbon films

Carbon films have been synthesized at room temperature in helium atmosphere, at high pressure, on (1 0 0) Si substrates by pulsed KrF excimer laser ablation of highly oriented pyrolitic graphite. By changing laser power density (from 8.5 to 19 MW mm⁻²) and gas pressure (from 0.6 Pa to 2 kPa), nanometer sized cluster assembled films were obtained. Film morphology, as studied by scanning electron microscopy, changes with increasing helium pressure, from dense columns, to node-like morphology, then to an open dendritic structure. Carbon coordination was studied by visible Raman spectroscopy in all films. They are structurally disordered, sp² coordinated and belong to the family of glass-like carbons. The deduced film coherence length agrees with the average size of carbon aggregates that build up the films, as measured by transmission electron microscopy in representative samples. The average number of carbon atoms per cluster, that depends on helium (high) pressure, was obtained by a simple model.     

Deposition of carbon nitride films by reactive pulsed-laser ablation at high fluences

The effects of high laser fluence on the properties of CN_x thin films prepared by reactive pulsed laser (KrF excimer laser, λ=248 nm, τ_FWHM=30 ns) ablation at two different N₂ gas pressures were investigated. A variety of analytical techniques have been used to characterize the structure and properties of the deposited films: X-ray photoelectron spectroscopy; X-ray diffraction; scanning electron microscopy; energy dispersive X-ray spectroscopy; Fourier transform infrared; and Rutherford backscattering spectroscopy. Analysis of these data shows the existence of a certain amount of covalent C–N single bonds and a nitrogen content up to 44%. The results also show the presence of covalent C≡N triple bonds in the film deposited at high nitrogen pressure (50 Pa).Comparison with the films deposited by XeCl excimer laser (λ=308 nm, τ_FWHM=30 ns), at the same experimental conditions, will also be presented.     

A negative resist for KrF excimer laser lithography

The design and preparation of a series of negative resists for KrF excimer laser lithography are described. Each resist is composed of poly(hydroxystyrene) and an aromatic azide. The base resin shows high transmittance of 62%/μm at 248 nm, when p-ethylphenyl p-azidophenylsulfonate. 4-azido-4α-methoxy-chalcone, 1-(4 azidobenzylidene)-3-(α-hydroxy-4-azidobenzyl)-indene, 4,4α-diazido-3,3α-dimethoxybiphenyl, or 1-(4-azidostyryl)-5, 5-dimethyl-2-cyclohexen-1-one is employed as a sensitizer. These azides are obtained by red-shifting the absorption maxima to lower energy regions than the exposing wavelength of 248 nm. Transmittance of resists can be controlled from 10 to 30%. The resist is exposed with a KrF excimer laser stepper and developed in an alkaline solution. Sensitivities of about 15 mJ/cm² are observed. A good, subhalf-micron resist profile is achieved. The photochemical reaction mechanisms of poly(hydroxystyrene) and 4,4α-diazido-3,3α-dimethoxybiphenyl were studied at 248 nm and 313 nm exposure. Quantum yield for photodecomposition at 248 nm is seven times larger than that at 313 nm, but dissolution-inhibition effects are larger at 313 nm exposure. Consequently, the resist shows higher sensitivity at 313 nm than at 248 nm.     

Evaluation research of polishing methods for large area diamond films produced by chemical vapor deposition

The current study compared several polishing techniques of chemical vapor deposition (CVD) diamond films. Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. In the present work, microwave plasma enhanced chemical vapor deposition (CVD) was used to obtain diamond films with full width half magnitude (FWHM) less than 10 wavenumbers at 1332 cm^− 1 Raman peak. The diamond films were processed through mechanical polishing, chemical-assisted mechanical polishing, thermo-chemical polishing, excimer laser ablation, and catalytic reaction assisted grinding. A profilometer, an atomic force microscope, and a scanning electron microscope have been used to evaluate the surface morphology of diamond films before and after polishing. The results obtained by using the above mentioned techniques were analyzed and compared.     

Application of laser ablation technique for removal of chemically inert organically modified silicate coatings

Removal of organically modified silicate (Ormosil) coatings from 2024-T3 aluminum alloy substrates has been investigated using a laser ablation technique utilizing a 308 nm excimer laser. Incorporation of UV-absorbing dye molecules containing λ_max in the vicinity of the laser wavelength (butyl-PBD, Furan 2, Morin, HQSA) into the Ormosil thin film was found to facilitate coating removal. Ormosil thin films containing 0.1–0.5 mol% UV-absorbing dye molecules were subjected to laser treatment at various fluences ranging from 0.2 to 0.6 J/cm². The presence of the UV-absorbing dye molecules in the Ormosil thin film was found to facilitate coating removal at a lower fluence as compared to dye-free coatings as determined by scanning electron microscopy. The effectiveness of coating removal was found to depend on several parameters including laser fluence, number of pulses per spot, and dye concentration.     

A high performance size exclusion chromatographic study on the depth-dependent gradient in the molecular weight of aged triterpenoid varnish films

The depth-profiles of aged triterpenoid resin films, dammar and mastic, were uncovered by optimized krypton fluoride excimer laser ablation (248 nm, 25 ns) and the etched varnishes were examined by high performance size exclusion chromatography (HP-SEC). The use of two detectors monitored the molecular weight distribution across depth as a function of absorbance at ultraviolet (240 nm) and visible (400 nm) light. The absorption of the films at both wavelengths is separated in a small fraction of sesquiterpenoids (200 Da), triterpenoid molecules (400/500 Da), dimerized and oxidized triterpenoid molecules (900–1000 Da) and condensed entities (10–80 kDa) that are formed upon the radical polymerization of polycadinene and cis-1,4-poly-β-myrcene, which are the polymers of dammar and mastic, respectively. The results establish the generation of depth-dependent gradients in radical polymerization, condensation and cross-linking across the depth-profiles of the triterpenoid films as a consequence of aging.     

Ultrafast deep UV lithography using excimer lasers

Various excimer laser wavelengths have been used, both in mid- and deep-UV regions—308 nanometers (nm) from XeCl, 249 nm from KrF and 222 nm from KrCl–to delineate images in a number of resists. The quality of the images obtained with the laser exposures, the absence of speckle, and the insignificant loss of resist reciprocity make excimer laser lithography an attractive technique. The ultrafast exposures possible with this method significantly lessen the sensitivity requirements on deep UV resists, making the choice of the resist more flexible.     

Laser‐induced surface structures on gold‐coated polymers: Influence of morphology on surface‐enhanced Raman scattering enhancement

The fabrication of highly sensitive and reproducible substrates for Surface‐Enhanced Raman Scattering (SERS) remains a challenging scientific and technological issue. In this work, laser‐induced periodic surface structures are generated on poly(trimethylen terephthalate) films upon laser irradiation with the linearly polarized beams of a Nd:YAG laser (4th harmonic, 266 nm), an ArF excimer laser (193 nm), and a Titanium:sapphire laser (795 nm), resulting in periods close to the laser wavelength when irradiating at normal incidence, and larger periods for different angles of incidence. Additional irradiation with a circularly polarized beam at 266 nm produces superficial circular structures. The nanostructured polymers are coated with a nanoparticle assembled gold layer by pulsed laser deposition at 213 nm. The capabilities of these substrates for SERS are evaluated using benzenethiol as a test molecule and different degrees of Raman signal enhancement are observed depending on the nanostructure type. The highest enhancement factor is obtained by for nanostructured substrates with the highest values of period, depth, and roughness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42770.     

Superhydrophobic graphene/ceramic templates for the preparation of particulate drugs

This paper proposes the use of superhydrophobic graphene/ceramic templates fabricated through laser texturing and patterning for the preparation of particulate drugs. A nanosecond pulse fiber laser was used to texture a graphene film coated on ceramic substrates for obtaining a superhydrophobic surface. Then, laser patterning was conducted on the laser-textured surface to define the diameter of the prepared particulate drugs. Laser-textured graphene/ceramic substrates with a laser areal fluence of 17.51 J/cm² and a hatch distance of 0.01 mm exhibited a maximum water contact angle of 151.5°. This result was obtained because the laser-textured graphene films contained coral reef structures with nanoscale pores. Raman analyses indicated that the intensities of the G and 2D bands gradually decreased after the laser texturing and patterning processes. Moreover, the sheet resistance of the laser-textured and laser-patterned graphene films was larger than that of untextured ones because the thickness of the graphene films was reduced through laser thinning. The maximum heating temperature of the graphene-based heater was 140 °C for an input direct current voltage of 36 V. In addition, graphene-based self-heating devices were developed and successfully used to dry liquid roflumilast.