Vanadium oxide (VOx) thin films were prepared on unheated glass substrate by pulsed dc reactive magnetron sputtering using different pulse frequency. Field emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE) measurements were made on the deposited VOx films to characterize the microstructure, composition and optical properties, respectively. It was found that under the same discharge power and argon-oxygen atmosphere, with the increase of pulse frequency, the vertical column-like structure in the films will gradually disappear and the ratio of high-valent VOx to low-valent VOx will obviously elevate. Optical parameters of the VOx films have been obtained by fitting the ellipsometric data (Ψ andΔ) using the Tauc-Lorentz dispersion relation and a multilayer model (air/roughness layer/VOx/glass). The results demonstrated that pulse frequency plays a critical role in determining the transmittance, refractive index, extinction coefficient and optical band gap etc. The correlations between the microstructure, composition, optical properties and pulse frequency are also given by our experiment results. And the mechanisms for the evolution of the microstructure, composition and optical properties with pulse frequency have been discussed. Overall, due to the pulse frequency had a great effect not only on the growth characteristics but also on the optical properties of the VOx films, thus through variation of the pulse frequency during deposition which provide a convenient and efficient approach to control and optimize the performances of the VOx films.
Vanadium oxide (VOx) films were deposited onto well cleaned glass substrates by bipolar pulsed reactive magnetron
sputtering at room temperature. Dependence of the structure, composition, optical and electrical properties of the films
on the pulsed power’s duty cycle has been investigated. The results from the X-ray diffraction (XRD) analysis show that
there was no remarkable change in the amorphous structure in the films with duty cycle can be observed. But chemical
analysis of the surface evaluated with x-ray photoelectron spectroscopy (XPS) indicates that decrease the duty cycle
favors to enhance the oxidation of the vanadium. The optical and electrical properties of the films were characterized by
spectroscopic ellipsometry and temperature dependent resistivity measurements, respectively. The evolution of the
transmittance, optical band gap, optical constants, resistivity and temperature coefficient of resistance (TCR) of the
deposited films with duty cycle was analyzed and discussed. In comparison with conventional DC sputtering, under the
same discharge atmosphere and power level, these parameters of the VOx films can be modified over a broad range by
duty cycle. Therefore adjusting the duty cycle during deposition, which is an effective way to control and optimize the
performances of the VOx film for various optoelectronic devices applications.
Vanadium oxide films were prepared onto glass and KBr substrates at various deposition temperatures by DC reactive
magnetron sputtering. X-Ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM), Fourier transform
infrared spectroscopy (FT-IR) were employed to analyze the VOx films, respectively. Experimental results indicated that
deposition temperature has a great impact on the surface morphology of vanadium oxide films. The XPS analysis
confirmed that the vanadium oxide films prepared are V2O5. From Fourier transform infrared spectroscopy, it can be see
that the infrared active mode corresponding to V-O-V stretching vibration and the stretching vibration of unshared V=O
bonds appeared at about 840 cm-1 and 915 cm-1 in the films formed at 240 , respectively. A shift in the peak position
towards higher frequency was found with increasing the deposition temperature which indicated that the films formed at
higher deposition temperature were structural disorder.
KEYWORDS: Thin films, Resistance, Temperature metrology, Vanadium, Sputter deposition, Oxides, Atomic force microscopy, Thin film deposition, Scattering, Thin film devices
The dependence of morphology and thermal resistance on the substrate temperature during the deposition of the
vanadium oxide thin films (VOx) was studied. Atomic-force microscopy (AFM) analysis results revealed that the
structural features of VOx thin films strongly depend on the substrate temperature. Analysis of square resistance and its
temperature dependence demonstrated that the difference of morphology introduced by substrate temperature plays an
important role on the electrical properties of the films. The width of the thermal resistance hysteresis loop was also
observed varied with the substrate temperature.
Vanadium oxide (VOx) thin films were deposited on different substrates by reactive DC magnetron sputtering. Silicon
substrate, Si3N4/Si substrate, glass substrate, and α-Al2O3 substrate were adopted in experiments. Results revealed that
the structural features of VOx thin films strongly depend on the substrates. Analysis of square resistance and its
temperature dependence demonstrated that the crystal structure and the growth mode of VOx films play important roles
in the film electrical properties. Experiments demonstrated that substrates have great influence on the growth mode and
thermal resistance properties of VOx thin films.
The performance of a optical component is greatly dependent on its surfaces. There are many ways to measure and
evaluate a surface so far, but actually no one knows exactly what a "real" surface likes, and thus makes some
measurement unexplainable. This paper develops a way to construct various synthetic surfaces. Referred to actual AFM
measurement, regular or irregular surfaces can be created and studied. Bumps, scratches, granules, profile errors and
other construction elements can be added to form a very complicated virtual surface. The number, size and distribution
of these elements can be changed, and if necessary, the surface roughness can be controlled in a specialized range. As
these surfaces are created synthetically, we know exactly what construction these surface contain. The height data of
created virtual surfaces can be transferred into the file that AFM instrument can read and handle. As a typical example, a
very complicated surface is created step by step in this paper, and its PSD for each step are calculated. This process
mikes it very clear how the surface component element affect its PSD function, and is benefit to our better understanding
of real surface construction.
Multilayer dielectric grating plays an important role in the laser inertial confinement fusion, which is fabricated by using
holographic lithography and ion beam etching. In this paper details the reactive ion beam etching of multilayer dielectric
grating with SiO2 as the top layer. The etching of SiO2 was carried out by a radio frequency reactive ion beam etcher
with CHF3 chemistry to increase the etch selectivity and get a high fidelity grating pattern transfer from photoresist into
SiO2 coating. The photoresist gratings with different profiles as masks were used to create SiO2 corrugations with
different profiles separately. The etching results were analyzed in detail, including the facet and redeposition effects. In
conclusion, it is essential that the photoresist grating mask should be high and steep enough to get SiO2 grating with
vertical profiles. The multilayer dielectric grating with SiO2 as the top layer exhibited an efficiency of about 95% in the - 1 order at TE polarization of 1 064 nm light at Littrow mounting.
The uniformity of ion beam current density profile has been amended by changing the flow of the gas and making a new
beam channel. The platform scanned in the horizontal orientation in this experiment, so the horizontal ion beam current
distribution had hardly any effect on the etching uniformity and amending the ion beam current density profile in the
vertical orientation was sufficient for the purpose of plat etching profile. The ratio of the ion source's working gas inputs
has some effect for the uniformity and a ratio of 6.50sccm: 8.00sccm: 9.60sccm of the three gas inputs flow1: flow2:
flow3 will lead to a more uniform profile. According to the horizontal distribution and the original vertical ion beam
current density distribution measured by Faraday Cup, a new beam channel was made. The uniformity of ion beam
current density profile is enhanced from ±4.31%to ±1.96% in this experiment.
A novel process that combines interference lithography and ion beam etching is presented for fabrication of magnetic
submicron structures and nanostructures in this paper. Instead of an antireflective coating, vertical standing wave
patterns were removed using oxygen descumming process. A series of magnetic submicronmeter structures were
fabricated on Co0.9Fe0.1 films by this technique. Fabrication of magnetic nanostructures was performed by using a high
exposure dose and modifications in optimized development conditions. A thin Au film was deposited on the sidewall of
the magnetic nanostructures to avoid the oxidation of Co and Fe. The effect of this method was confirmed by X-ray
photoelectron spectroscopy (XPS). Hysteresis loops measured by a highly sensitive superconducting quantum
interference device (SQUID) technique show the different magnetic properties of the magnetic patterns with different
critical dimensions.
It is known that rectangular grooves profile and various duty cycles (line to pitch) are required to attain maximum
efficiency. The gold transmission phase gratings have been fabricated using holography and ion-beam etching
techniques. The latent image monitoring technique and real time end-point detection technique were utilized to improve
control of the shape of grooves and duty cycle during exposure and development, respectively. It is difficult to produce
gratings with larger duty cycle in photoresist on gold for standing wave, nevertheless it is revealed in our work that the
duty cycle can be more than 0.4 for the case for photoresist on gold substrates if development is stopped where the slope
of the monitoring curve begins to drop off, not at the peak of the diffracted signal. In ion-beam milling, the influence of
redeposition on the shape of grooves and duty cycle has been overcome by using a thin mask of Chromium with a
comparatively low ion-etch rate and tilting and rotating substrates beneath the ion beam. Finally, some gold phase
gratings with the duty cycles in the range of 0.25-0.45 have been obtained, whose duty cycle value is about 0.45, and
their grooves profile is trapezoidal profile whose left and right facets are both more than 83 degrees approximately.
KEYWORDS: Surface roughness, Atomic force microscopy, Silicon, Spatial frequencies, Glasses, Data acquisition, Probability theory, Spectral data processing, Silica, Semiconducting wafers
This paper presents a comparative studied of surface roughness. Samples were first measured by atomic force microscope (AFM). The acquired height data was then processed to calculate their power spectral density (PSD) and multi-fractal spectrum (MFS). The calculation results indicate that MFS of different samples with same sampling length differs significantly from each other, while the MFS of the same sample with different sampling length or different sampling position is quite similar. The calculation also shows that MFS is very sensitive to particles or scratches appeared on the surface. The PSD of the same data acquired from these samples are also presented for comparison. It is clear from the calculation results that the PSD curves vary with the sampling position and sampling length, thus makes the evaluation uncertain. No quantitative index available from PSD, only qualitative information obtained. Comparatively, MFS is better in description of a surface roughness.
Parameters of two spherical waves are firstly optimized to get the exact groove densities of diffractive gratings.
Consequently, the groove density differences between on the plane and on the curved substrates are derived. Therefore,
some experimental results are provided to demonstrate the validity of this method above. Meanwhile, the curvatures of
the substrates are measured three times by using long trace profiler (LTP), which assures the repeatability of the bending
technique for grating substrates. At last, the advantage of this method is exhibited through comparing the errors of
grating groove density fabricated by this technique with only two spherical waves.
Magnetic submicron meter structures were fabricated on Co0.9Fe0.1 films by laser interference lithography combined with
ion beam etching. The vertical standing wave was restrained by using proper exposure dose and appropriate development
time. Hysteresis loops of the magnetic film and magnetic patterns were presented by surface magneto-optical Kerr effect.
The difference magnetism between magnetic patterns with different critical sizes and the film was discussed.
The major etching processes of a large-aperture multilayer diffraction grating, including the uniformity of the ion beam
current along the major axis and the on-line measurement of the diffraction intensity distribution are described. A large-aperture
ion beam etcher with radio frequency linear source has been developed to fabricate large-aperture diffractive
optical elements. The length with ±5.1% uniformity of the ion beam current distribution along the major axis is 30 cm. A
series of multilayer diffraction gratings were etched successfully by using this etcher with CHF3 chemistry. Multilayer
diffraction gratings on a 80 mm×150 mm BK7 substrate etched for laser systems are shown. The grating exhibits an
averaged diffraction efficiency about 96% at TE polarization of 1 064 nm light viewed at Littrow angle.
A binary transmission phase grating is designed to operate as a dispersive element used in soft x-ray plasma diagnostic in ICF (inertial confinement fusion). The first and zero orders diffraction efficiency is simulated as a function of wave length and grating thickness. It is shown that the first order diffraction efficiency of a transmission phase grating can be up to 23.3% of the incident light, whereas that is not more than 10% for a conventional amplitude transmission grating. The transmission phase grating is fabricated in gold film supported by polyimide membranes using holography and ion beam etching method. The primary experimental results are presented.
Diffraction gratings are designed for grazing-incidence operation in the soft x-ray spectral region. The efficiencies for various diffraction orders are simulated as a function of angle of incidence and blazed angles. According to the beat phenomenon, the grating pattern with double-frequency on the same substrate is recorded in a holographic way. The blazed grating will be fabricated using holography and ion beam etching method. The primary experimental results are presented. This kind of blazed grating is a key element used as a beam splitter of soft x-ray Mach-Zehnder interferometer, which is a new tool to diagnose the plasma generated by the laser-based inertial confinement fusion.
Holographic and ion beam etching technique has become routine means for fabricating vacuum ultraviolet and soft x-ray diffraction gratings. A novel technique has been successfully, in which oxygen reactive ions etching was used to achieve resist ashing of the grating, to fabricate diffraction gratings with holographic ion beam etching. The new technique was used to fabricate a spherical blazed grating, 1200g/mm and 130 nm blazed wavelength, and some laminar gratings for monochromators in the beamline of National Synchrotron Radiation Laboratory. The results show that the new technique can considerably lower the stringent requirements of holographic exposure and development, and makes it controllable to make smooth grooves with desirable depth and duty cycle. A gold transmission grating is one of the critical elements in the soft x-ray spectrometer for plasma diagnostics. With holographic-ion beam etching technique, a number of self-supporting transmission gratings have been fabricated for inertial confinement fusion (ICF) diagnosis.
Variable Line-Space gratings play an important role in focusing and aberration-reduced. They are widely used in spatial spectrum and synchrotron radiation facilities. However the design and fabrication methods of them are difficult. The problem is to be able to record holographically the expected grooves distribution. The geometric theory of aspheric wave-front recording optics is briefly described. We introduce the genetic algorithm to the parameters optimization of holographic variable line-space gratings. In order to obtain a steady set of recording parameters, we propose that the objective function of the genetic algorithm should consider the effect of the recording parameters errors. The integral expression of the objective function is also derived to improve the efficiency of calculation. Design example of holographic variable line-space plane gratings for a position sensor is given to demonstrate the capability of this method. The line-profiles of variable line-space plane gratings with different recording parameters are also compared in this paper.
A number of current and future optical and optoelectronic devices require the creation of structure in HfO2 film. The reactive ion beam etching of HfO2 film and photoresist mask in Ar/CHF3 gas mixture was examined as a function of ion energy, discharge composition and ion beam incident angle. The details of etch rate have been interpreted in terms of mechanism of etching. The etch rate has shown a square root dependence on ion energy and variation versus incidence angle. The CHF3- plasma produced some chemical enhancement in HfO2 film etching. Compared with pure argon etching, better selectivity and higher fidelity pattern transfer were achieved with Ar/CHF3 for HfO2 film over photoresisit mask. The AFM scans of etched HfO2 film by tapping mode showed good surface quality.
Ronchi gratings are widely used as beam splitters in interferometry. The phase Ronchi gratings are fabricated in K9 (or BK7) substrates using a photolithographic process and ion beam etching process. The geometry of the gratings was determined within the approximations of the scalar diffraction theory to minimize their diffraction intensities in 0 and 2 orders at 514.5nm. Their diffractive characteristics are measured using Ar+ laser at 514.5 and 496.5nm. The phase Ronchi gratings exhibit the diffraction intensity in 0 or 2 order to be three orders of magnitude less than that in 1 order.
Soft x-ray condenser zone plates are one of the most essential condensing and dispersing elements in the field of soft x-ray microscopy. The zone-plates are used at 3.2nm, whose diameters are 2.8mm. The widths of their outermost zone are 647nm. The zone plate is made of Au. Self-supporting zone plates are fabricated by holography-ion beam etching process to obtain x-ray lithography mask, the x-ray lithography, photolithography and micro electroplating process were used to obtain their self-supporting structure. The self-supporting zone plates are free of membrane absorption and degradation.
With holographic-ion beam etching technique, a number of self-supporting transmission gratings have been fabricated for inertial confinement fusion diagnosis. In addition to the general process, a practical method for monitoring the evolution of the grating structures exposed in photoresist during development of the resist. The real-time monitor technique developed here is relatively simple in comparison with a He-Ne laser and detector, which needs delicate control.
We present the recent advances achieved in the Changchun Institute of Optics and Fine Mechanics, Chinese Academy of Science, in the field of the soft X-ray etched multilayer optics. In the present study, Mo and Si have been chosen as materials for the scattering layer and space layer soft X-ray multilayer, respectively. The fabrication of Mo/Si multilayer used by the magnetron sputtering, the patterned resist was obtained by optical holography, and the pattern of the resist was transferred into the multilayer by the ion beam etching. The several components based on soft X-ray etched multilayer were measured by grazing incidence X-ray reflectance measurements at (lambda) equals 0.154 nm (Cu-K(alpha )) using a conventional diffractometer.
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