fully understood, it is necessary to know the refractive index (n) and the extinction coefficient (k). Spectroscopic ellips- ometry (SE) is a powerful non-destructive technique to mea- sure the opticalproperties of thinfilms. In SE, the wavelength dependent optical constants and the thickness of thinfilms can be determined by analyzing the change in the polarization state of the reflected light from the film surface and developing an optical dispersion model of the film
In this paper, we report how a quantity, the anisotropic surface excess function (ASEF), can be extracted directly from the measured signal. The great advantage of the ASEF is it is dominated by the opticalproperties of the plasmonic layer only. Thin plasmonic structures with in-plane anisotropy can be measured, the only limit to the approach being that the substrate must be optically isotropic. As amorphous materials, such as glass, or tetragonal unit-cell single-crystal structures satisfy this condition, the latter is not a major limitation for the approach. The full investigation of plasmonic resonances that this approach allows produces additional constraints in the
Variable angle spectroscopicellipsometry (VASE) measurements were performed using a J.A. Woollam Co. Inc. model M-2000D variable angle spectroscopic ellipsometer to estimate sample thickness and opticalproperties of pp–GT thinfilms . The refractive index n, extinction coefficient k and thickness were derived from the experimental Δ and Ψ data via regression analysis. The relation between n and thickness for the polymer samples has also been investigated. UV-Vis spectroscopy measurements were performed using an Avantes Avaspec-2048 spectroscopy unit with an Avalight-DHc light source to measure the absorbance in the ultraviolet and visible region. From those data, values of optical band gap have been derived. Surface morphology and roughness parameters of pp–GT thinfilms fabricated under different RF powers were determined from atomic force microscope (AFM) images acquired on a NT-MDT NTEGRA Prima AFM operating in semi-contact mode. A Hysitron Triboscope was used to perform the nanoindentation study. During the nanoindentation study, a Berkovich indenter (70.3° equivalent semi-opening angle) was used and instrument compliance was calibrated using fused silica. Preliminary images of the samples under investigations were collected in order to evaluate the roughness of the area to be indented. Twelve indentations were made on each sample and the results presented are an average of these indentations. Typical loads used in the indentation ranged from 100 μN to 2000 μN with fixed loading time and hold time of between 2 and 5 s.
The optical constants are very important to designing the optical devises, because of their relation to the electronic polarize-ability of ions and the local field inside materials . Thus it’s important to determine the refractive index (n) and extinction coefficient (k) of the films. The dielectric function can be determinate from the optical parameters (n) and (k) by:
The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopicellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.
The formation of high-k thin ﬁlms by pulsed-source metal-organic chemical vapor deposition (MOCVD) has been investigated with in situ spectroscopicellipsometry. It is demonstrated that spectroscopicellipsometry is an eﬀective method for in situ monitoring of the fabrication of high-k dielectric thin ﬁlms with thicknesses of several nm’s. Thin yttrium oxide ﬁlms with average roughnesses smaller than the thickness of a single molecular layer, and with a capacitance equivalent thickness 1:7 nm were obtained. Thicknesses and opticalproperties of each individual layer were also extracted from spectroscopicellipsometry, by ﬁtting to appropriate structural models. [DOI: 10.1143/JJAP.42.1957]
Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thinfilms enhances the significance of surface interactions and charging effects requiring new understanding. Here we use micro-photoluminescence (PL) and ultrasonic force microscopy to explore the influence of the dielectric environment on opticalproperties of a few monolayer MoS 2 films. PL spectra for MoS 2 films deposited on
As shown in Figure 8, the direct band gap energy decreases progressively from about 3.65 to 2.75 with increasing in concentration values from 0.25 to 1 M. The decrease of optical band gap could be attributed to the structural and morphological change as well as the stoichiometric deviations in the film, which gave rise to the formation of located states in the band gap region. Other possibilities to explain this change in optical band gap could be related to the increase in particle size and this is well known for colloidal semiconductors [17, 18].
fundamental absorption. In addition, difference in absorbance can be observed clearly at wavelength shorter than 400 nm. One can note that the substrate temperature effect is clearly observed in the layer quality such as in the average between 370-390 nm; blue shift of the absorption edge was observed as function of substrate temperature until 400 °C revealing Burstein-Moss effect  as it mentioned in the inset of Fig. 1, which indicates that the increasing of doping amount can change the lattice structure. We are noting that the temperature effect is clearly observed in the layer quality. These results show that the produced ZnO thinfilms could be used in solar cells due to the low absorbance in the visible region [15, 21].
For the preparation of ternary compound semiconductors (PbSe) x (PbS) 1-x the constituent compounds PbSe and PbS have been taken in molecular stiochiometry proportional weights and crushed and mixed homogeneously. The different sets of samples of varying compositions (x = 0.1 to 0.9) were deposited on to the amor phous precleaned glass substrates at room temperature 308 K. All the samples are deposited under the similar optimized conditions. The thicknesses of films were controlled by using quartz crystal thickness monitor model No. DTM-101 provided by Hind-High Vac. The deposition rate was maintained 10-15 Å/ sec constant throughout sample preparations. These samples were annealed at reduced pressure of 0.1 micron for the duration of 4 hours at the temperature of 373 K and maintained carefully. These samples were then used for different characterizations.
Dye lasers are the most versatile class of lasers with di- verse applications in many scientific, industrial, medical and military applications, ranging from spectroscopy to potential counter measure devices. There is a growing devote concerning of dye laser and the search for par- ticular laser dyes that provide high laser damage thres- hold and high photostability. The photophysical and las- ing properties of laser dyes in liquid solutions show a strong dependence on the molecular structure of the dye [1-5]. Moreover, adequate substituent in the molecular core can alter both electronic absorption and emission maxi- mum due to change in mobility of electrons by the nature of the substituent group in the parent dye [6-11]. This structure modification may give rise to large changes in the photophysical and opticalproperties [12-24]. For exam- ple displacing the emission band to longer wavelengths can be achieved by: 1) attaching electron-donating group to the dye core ; 2) rigidifying the structure [26-28]; or 3) extending the conjugation of the chromophore [29-31]. So, lasing properties should be redetermined.
We have investigated the nonlinear opticalproperties, optical limiting thresholds, and figures of merits for five different phthalocyanine thinfilms, achieved through doping in PMMA polymer, using the Z-scan technique at 800 nm with 2 ps laser pulse excitation. From the open-aperture Z-scan data we derived that these molecules exhibit strong two photon absorption (2PA) with the nonlinear absorption coefficients in the range of 15 - 200 cm/GW. We have also estimated the sign and magnitude of real part of third order nonlinearity through the closed aperture data. Preliminary femtose- cond pump- probe data suggests that the lifetimes of excited states are in the sub-100 ps regime for all the molecules in film form. Our studies provide concrete evidence that these phthalocyanines are prospective candidates for mul- ti-photon imaging and optical limiting applications.
The XRD profiles show that the crystalline quality of the ZnO films have deteriorated with indium doping. As the concentration of indium increases the intensity of 002 peak decreases and growth appeared in 100 and 101 directions. Beyond indium doping level of 4 at% the preferred orientation of the films switched from 002 to 101 direction. Similar behavior of crystalline nature on extrinsic doping has been reported earlier 16,17,18 . During the film growth the presence of dopant atoms will induce a difference in reactions occurring on the substrate surface. This brings changes in the surface free energy and the direction of film growth 19 . For further understanding of the effect of indium doping on the crystalline
In the present investigation, chemical spray deposition technique (SPT) was used to grow undoped ZnO thinfilms on glass substrates by varying the substrate temperature. The influence substrate temperature on the structural and opticalproperties investigated here was found to be significant. The XRD results show the presence of the ZnO wurtzite phase with preferential orientation (002) of the film growth along the c-axis, concerning the deposited layer at 100°C, which presents a phase totally amorphous. The average crystalline size increases with increase in substrate temperature indicating better crystallinity of films deposited at higher substrate temperature (300°C) as the films become more uniform and dense, grain size is varied with substrate temperature from 10 to 28 nm. The optical transmittance of polycrystalline films was varied from 60% to 85% in the visible region. The obtained optical gap values for the different substrate temperature are in good agreement with the data of literature (3.67-3.25eV).
electrode and has a transparent electrode for a display, a solar cell, a transparent warm element, and an electric element. The SnO2 thin film is fabricated by shower, synthetic vapor testimony, and sputtering. It can be fabricated in huge sums by sputtering, making the items more affordable. Notwithstanding, those produced by sputtering have defects caused by variety in temperature, affidavit time, measure of oxygen in the chamber, measure of plasma created (attributable to the adjustment in the supply control power), and vacuum in the chamber. The underlying condition of the substrate when a thin film develops can influence the electrical and opticalproperties of the thin film. Along these lines, so as to enhance the electrical and opticalproperties of the SnO 2 thin film, it is
concentration precursor solution was 0.15 M/L. Depositions were done at 350˚C on cleaned glass substrates. X-ray dif- fraction technique (XRD) studies for all the prepared film; all the films are crystalline with hexagonal structure .The opticalproperties of the prepared films were studied using measurements from VIS-UV-IR spectrophotometer at wave- length with the range 300 - 900 nm; the average transmission of the minimum doping ratio (Zn at 0.1%) was about 55% in the VIS region, it was decrease at the increasing of Zn concentration in the CdS films, The band gap of the doped CdS films was varied as 3.7, 3.8, 3.6 eV at x = 0.1, 0.3 and 0.5 respectively.
It is found that prolonged growth experiments led to slightly rougher films, with Rms values only ranging from 6.2 to 10.5 nm as the film thickness increased (Table 3). This in turn implies that increasing film thickness (36 – 88 nm) does not have a profound effect on the roughness properties of the samples. However, resulting samples did show marked thermochromic behaviour and their values significantly reduced in IR region (Figure S3). The Δ T values determined were 52.9, 82.6 and 95.9 % for 60, 90 and 120 sec, respectively (Table
Figure 1 shows the SEM micrograph of both undoped and doped IZO films with 11.0kx magnification. Undoped films have smooth, closely packed grains which are uniformly distributed. When Indium (1%) was incorporated, the morphology changes to well defined nano fibers forming chain throughout the surface .The average width of the nano fibre was measured as 440nm. As the concentration of the dopant increases the surface becomes broken chain like nano structure. When the In concentration reaches 5% the morphology modified to spherical shaped particles spread throughout the surface.
to 450˚C showing semiconductor behavior. The lowest resistivity value 5.3 × 10 − 5 Ω-cm has been obtained for annealed film at temperature of 450˚C. It is ob- servable also that, the carriers mobility increased with increase in annealing temperature. This may be due to the increase of the grain size with increase in annealing temperature, and this leads to reduction of the grain boundary scat- tering due to charge carriers. The decrease of the electrical resistivity of annealed films is due the increase of the mobility carriers.
illustrate the cross-section TEM image and the composition analysis by EDX for the HfO 2 thinfilms under investigation. In the TEM images shown in Fig. 6, we confirmed that the total thickness of the film and that of the interfacial layer were approximately 6.9 and 2.1 nm, respectively, which are in good agreement with 2.0 and 6.2 nm estimated from the SE spectra. Furthermore, we found from the element distri- bution profiles across the film obtained by using EDX analy- sis that the concentrations of Hf and O increase in the inter- facial layer region while the concentration of Si decreases gradually in the direction from the substrate to the surface 共具 1 典→ 具 2 典兲 . Above the interfacial layer the concentrations of Hf and O are relatively high while the concentration of Si is virtually zero. The interfacial layer is supposed to be a Hf x Si y O z layer in which the ratio of Hf to Si 共 x / y 兲 increased gradually, and the upper layer is mainly composed of HfO 2 . FIG. 4. (a) Photon energy dependence of average dielectric constants mea-