Roughness Of Thin Films Research Articles

Y2O3 optical constants between 5 nm and 50 nm.

We report optical constants of e-beam evaporated yttrium oxide Y2O3 thin films as determined from angle-dependent reflectance measurements at wavelengths from 5 to 50 nm. Samples were measured using synchrotron radiation at the Advanced Light Source. The experimental reflectance data were fit to obtain values for the index of refraction and thin film roughness. We compare our computed constants with those of previous researchers and those computed using the independent atom approximation from the CXRO website. We found that the index of refraction near 36 nm is much lower than previous data from Tomiki as reported by Palik. The real part of the optical constants is about 10% to 15% below CXRO values for wavelengths between 17 nm and 30 nm. Films were also characterized chemically, structurally, and optically by ellipsometry and atomic force microscopy.

Study the structural and optical properties of titanium oxide thin film, doped with chromium prepared in Sol-Gel method

This paper presents the effect of Cr doping on the optical and structural properties of TiO2 films synthesized by sol-gel and deposited by the dip- coating technique. The characteristics of pure and Cr-doped TiO2 were studied by absorption and X-ray diffraction measurement. The spectrum of UV absorption of TiO2 chromium concentrations indicates a red shift; therefore, the energy gap decreases with increased doping. The minimum value of energy gap (2.5 eV) is found at concentration of 4 %. XRD measurements show that the anatase phase is shown for all thin films. Surface morphology measurement by atomic force microscope (AFM) showed that the roughness of thin films decrease with doping and has a minimum value with 4 wt % doping ratio.

P-Si(100)/InGaN thin film structure and investigation of its physical properties: N2 gas flow effect

Abstract In this study, effect of N2 gas flow rates on structural, optical and morphological properties of InGaN thin films grown by Radio Frequency Magnetron Sputtering (RFMS) method on p-Si (100) substrate have been investigated. X-ray diffraction (XRD) measurements confirmed that InGaN thin films have been successfully deposited and exhibited diffraction peak belong to (002) plane for each film. The surface roughness of InGaN thin films has been determined by using Atomic Force Microscopy (AFM) and the roughness value is about 13 nm with a maximum height of 36 nm and a maximum depth of 37 nm. The surface roughness value Rq\RMS value is 15 nm, which is almost consistent with the linear roughness value for 0 sccm. The energy band gap of the film was determined by using the optical reflectance spectra and the value of the band gap energy is found to be 2.01, 1.77 eV and 2.26 eV for 0 sccm, 1 sccm and 2 sccm N2 gas flow rates, respectively

Microstructure and mechanical properties of sputtered Aluminum thin films

The microstructure, surface roughness and mechanical properties of aluminum thin films deposited by rf magnetron sputtering are presented. The films were sputtered on stainless steel substrates at varying rf powers of 150 W, 200 W, 300 W and 350 W at a deposition time of 2 hours and at a substrate temperature of 90oC. The microstructure at 200 W shows fine, well-defined and homogeneous distributed grains. The lowest surface roughness is at the power of 150 W whereas the highest is at 250 W. The highest modulus, hardness and lowest depth of penetration are obtained at 200 W. The results indicate no direct relationship among rf power, mechanical, roughness and microstructure of Al thin films deposited at substrate temperature of 90oC. As such, optimization of the sputtering process for rf power is necessary for deposition of quality Al films on metals.

Structural and Optical Studies of Cadmium Sulfide Quantum Dot-Graphene Oxide-Chitosan Nanocomposite Thin Film as a Novel SPR Spectroscopy Active Layer

The aim of this study is to prepare and study the cadmium sulfide quantum dot-graphene oxide-chitosan composite thin film. This composite material was coated on top of the gold layer by a spin-coating technique as a modification of the active layer for metal ion sensing using surface plasmon resonance spectroscopy (SPR). The composite material was prepared using a simple wet solution mixing method. An atomic force microscope (AFM) shows that the addition of GO increased the roughness of the composite thin film and the presence of CdS QDs cannot be observed as the size of the QDs are very small. The morphology of the nanocomposite material was observed using transmission electron microscopy (TEM). From the TEM images, it is observed that the materials mixed to form a nanocomposite material. The optical properties of the thin film via UV-Vis spectroscopy shows that the absorbance peaks of the thin film can be observed around 220 nm to near 300 nm, and the band gaps are around 4.0 eV. Lastly, the prepared thin film was tested as an active layer for metal ion detection via surface plasmon resonance (SPR), where the angle shift was observed to show that the prepared thin film has high potential for Co2+ ion detection.

Optimal target sputtering mode for aluminum nitride thin film deposition by high power pulsed magnetron sputtering

Low surface roughness, low residual stress, and (002) textured aluminum nitride (AlN) thin films are favored for applications in microelectronic and optoelectronic devices. In this paper, AlN thin films were deposited by reactive high power pulsed magnetron sputtering (HPPMS). The effect of aluminum target sputtering mode and sputtering power on thin film residual stress, crystalline structure, surface roughness, and morphology of AlN thin films was studied. The results indicate that, with Al target sputtering mode transfer from metallic mode to transitional and compound modes, respectively, the number of Al species decrease, and ion-to-neutral ratio of Al species increase. Comparing the AlN thin film deposited in compound mode with that deposited in transitional mode, the latter exhibited lower surface roughness and residual stress. In addition, AlN thin film with (002) texture and lower residual stress is obtained by increasing sputtering power in transitional mode. For fabricating AlN film via reactive HPPMS with a particular (002) texture, low surface roughness, and residual stress, sputtering the target in the transitional mode with high sputtering power is optimal.

Modification of the structural and optical properties of Fe-doped SnS2 thin film

Undoped and Fe- doped tin disulfide (SnS2: Fe) thin films were deposited onto soda- lime glass substrates from aqueous solution by spray pyrolysis technique. The molar concentration of Fe ions varied from 0 to 15% in the initial solution. X-ray diffraction investigation revealed that all the films were formed in a polycrystalline, hexagonal structure. SEM micrograph showed that doping with iron compressed the SnS2 grains and reduced their size remarkably. Energy dispersive x-ray analysis (EDAX) proved the presence of iron in the thin films. It was found that the average roughness of the SnS2 thin film increased from 1.1 to 2.8 nm after doping with iron. Investigation of optical data revealed that the absorption coefficient of the samples was improved by introducing Fe ions into SnS2 lattice. In addition, the band gap of SnS2 thin film decreased from 2.55 to 2.44 eV as the Fe concentration increased up to 15%.

Effect of gamma irradiation dose on the structure and pH sensitivity of ITO thin films in extended gate field effect transistor

Abstract Even though several studies have demonstrated the use of Indium Tin Oxides (ITO) as an extended gate field effect transistor (EGFET), the effect of different doses of gamma radiation on the intrinsic properties of the ITO films has not been considered. This study investigates the effect of gamma irradiation on the structural, optical, morphological and electrical properties as well as pH sensitivity (as an extended gate field effect transistor) of ITO thin films. ITO thin films with thickness of 400 nm were prepared using a radio frequency sputtering technique. The samples were then subjected to various doses of gamma radiation from a Co-60 radio-isotope (0.5 kGy, 1 kGy, 1.5 kGy, and 2 kGy). The structural and morphological changes as well as transmission and absorption of the thin films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field-Emission Scanning Electron Microscope (FESEM) and UV–Vis spectrophotometry, before and after irradiation. The irradiated ITO thin films were then used as an extended gate field effect transistor to determine its ability to improve sensitivity as pH sensors. The grain size and transmittance in the range 300–900 nm of the ITO films were found to decrease with increasing gamma irradiation dose. In contrast, the uniformity and surface roughness of ITO thin films increased with increasing gamma radiation dose due to the formation of lattice defects. Moreover, the electrical resistance of the thin films increased with increasing dose because of the low current density and high number of surface defects associated with irradiation. The pH sensitivity of the ITO thin films improved after irradiation, possibly due to the concomitant increase in surface roughness with increasing radiation dose. The improvements in the pH sensitivity of ITO thin films after irradiation justify their potential use as pH sensors.

Influence of deposition procedure on the properties of multiferroic BiFeO3-based thin films deposited by radio frequency sputtering

Two samples of Bi1−xBax(Fe1−xTix)O3 with x = 0.1 thin films were deposited by RF sputtering method, on commercial indium tin oxide∕glass substrates, using different deposition procedures. The effects of deposition conditions on the structural, magnetic and electrical properties of the thin films are studied. X-ray diffraction, scanning electron microscopy (SEM), dielectric and magnetic characterization techniques were performed at room temperature. The results show that the two samples exhibit rhombohedral perovskite structure without the presence of undesired phases of mixed iron bismuth oxides. The SEM micrographs reveal a huge difference in grain size between the films obtained by the two distinct deposition procedure. The analysis of the reflection and transmission spectra in the UV–vis range allowed us to determine the thickness and roughness of thin films synthesized. Also, from this analysis, the optical band-gap energy increases compared with that obtained for this doped compound in volume and with pure BiFeO3.

Inmovilización de la proteína fotoactiva bacteriorodopsina sobre óxido de zinc Aplicación en Celdas Solares Bio-Sensibilizadas

En este proyecto se construyeron fotoánodos para celdas solares sensibilizadas utilizando la proteína fotoactiva bacteriorodopsina (BR). El objetivo fue utilizar la proteína como sustituyente a los colorantes comunes a base de Ru, que son costosos y tóxicos. Los sustratos se prepararon recubriendo vidrio conductor con nanopartículas de óxido de zinc (ZnO-NPs). La proteína se inmovilizó en estos sustratos para completar un fotoánodo capaz de capturar la energía solar y transformarla en energía eléctrica. Las técnicas de dropcasting (DC), funcionalización química con feniltrietoxisilano (PTES) y la sedimentación electroforética (SE) fueron optimizadas para inmovilizar la proteína. Mediante espectroscopia de absorción ultravioleta-visible (UV-Vis) se demostró que la proteína conservaba su función fotoactiva después de la inmovilización. La resistencia y tasa de transferencia de carga del fotoánodo en el electrolito fue comparada por medio de impedancia electroquímica. Para los tres métodos se encontraron valores relativamente altos (105 Ω) en comparación con datos reportados para tintes de rutenio. El desempeño de los fotoánodos preparados por DC y SE en celdas solares sensibilizadas se determinó por cronopotenciometría bajo iluminación. Se encontró que la capa molecular de PTES permite inmovilizar la proteína en periodos más cortos de tiempo pero introduce una resistencia eléctrica adicional en el sistema, por lo que no es apropiada para el sistema fotoelectroquímico estudiado. Los fotoánodos preparados por SE permite obtener el fotovoltaje más alto (16 mV) y la tasa de transferencia electrónica más veloz, mientras que usando la técnica DC se midieron fotovoltajes de tan solo 1 mV. Estas respuestas sugieren que la orientación de la proteína en el ZnO es determinante en la fotorespuesta de la celda, ya que bajo el campo eléctrico aplicado durante SE la proteína se orienta según su dipolo eléctrico, mientras en el DC, la orientación es aleatoria. En base a los resultados obtenidos, se recomienda controlar mejor el espesor de la capa de la proteína, utilizar un electrolito más afín a la naturaleza de esta biomolécula y disminuir la rugosidad de la capa de ZnO para producir fotoánodos que transformen la energía solar de forma más eficiente.

Tin(IV) Substitution in (CH3NH3)3Sb2I9: Toward Low-Band-Gap Defect-Ordered Hybrid Perovskite Solar Cells.

The prevailing issue of wide optical gap in defect-ordered hybrid iodide perovskites has been addressed in this effort by heterovalent substitution at the metal site. With the introduction of Sn4+ in the (CH3NH3)3Sb2I9 structure, we have successfully lowered the pristine optical gap (2 eV) of the perovskite to a close-to optimum one (1.55 eV). Upon such heterovalent substitution, a gradual shift in the type of electronic conduction of the perovskites was observed. As evidenced from scanning tunneling spectroscopy and correspondingly density-of-state spectra, a significant shift of Fermi energy toward the conduction band edge occurred with an increase in the tin content in the host perovskite. This shift has resulted in tuning of the type of electronic conductivity from p-type to n-type and more importantly led to a better band alignment with the selective contacts of p-i-n heterojunctions. However, tin inclusion affected the surface roughness of the perovskite film in an adverse manner. Hence, the tin content was optimized by considering both the factors, namely, the band gap of the material and the surface roughness of thin films. In an energy-level-optimized planar heterojunction device, the short-circuit current density excelled with a power conversion efficiency of 2.69%.

Novel rare earth Gd and Al co-doped ZnO thin films prepared by nebulizer spray method for optoelectronic applications

In this study, for the first time, rare earth element gadolinium and aluminum co-doped zinc oxide (Gd:AZO) films were prepared on insulating glass plates using cost-effective nebulizer spray method with various Gd co-doping levels (0, 0.5, 1 and 1.5 at.%). The deposited films were characterized using X-ray diffraction, FT-Raman, AFM, EDAX, UV-VIS spectroscopy, Photoluminescence (PL) spectrum and Hall Effect measurement at room temperature. From XRD study, it is confirmed that the Gd and Al ions are incorporated into ZnO lattice. Film crystallinity is slightly reduced due to Gd content by increasing lattice defects. Topology of AFM images displays a slight increase of Gd:AZO thin film roughness from 20 nm to 36 nm, with an increase of thickness from 232 to 324 nm respectively. Elemental mapping and EDAX studies confirmed the existence of Zn, O, Al and Gd elements in the prepared Gd:AZO thin films. Spray deposited pristine AZO films showed maximum optical transmittance ∼91% in entire wavelength spectrum and energy gap value ∼3.31eV. The observed PL spectra showed as a UV emission at 387 nm for deposited films. The obtained minimum resistivity and maximum figure of merit values are 3.42 × 10−4Ωcm, and 18.68 × 10−3(Ω/sq)−1, respectively for 1.5 at.% Gd co-doped AZO thin film. Both values are decent enough for opto-electronic devices.

Plasma nanotexturing of amorphous carbon films by reactive ion etching

Amorphous carbon thin films were grown by magnetron sputtering on crystalline Si and fluorine-doped tin oxide (FTO) substrates and annealed at 600 °C in vacuum. Subsequently, the films were subjected to SF6 plasma nanotexturing processes using different secondary gases such as H2, O2, and Ar. The samples were characterized by profilometry, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and contact angle measurement. The samples have shown nanostructured surface patterns that strongly depended on the secondary plasma gas used (H2, O2, or Ar); the films subjected to the SF6 + Ar plasma nanotexturing presented the highest surface roughness. Investigation of the atomic structure indicated that the annealing process is responsible for a significant increase in sp2 hybridization of C. The contact angle measurement results have revealed the hydrophilic to hydrophobic transition owing to the annealing process. In contrast, super hydrophilic behavior was observed after the plasma nanotexturing processes. The increase in both the surface roughness and hydrophilicity of these nanotextured carbon thin films are highly desirable characteristics for their application as counter-electrodes in dye-sensitized solar cells and batteries.

Effect of sulfur quantity in post-treatment on physicals and electrical properties of electrodeposited Kesterite Cu2ZnSnS4 thin films

In this work, thin films of Cu2ZnSnS4 (CZTS) have been successfully electrodeposited onto FTO substrate. The films are post-sulfurized with different amount of sulfur varied from 0 to 0.5 g at 550 °C under N2 atmosphere. Effect of sulfur quantity during the annealing treatment on structural, morphological, optical and electrical properties of CZTS films have been investigated using various techniques. XRD analysis shows that CZTS thin film annealed at 550 °C in the presence of 0.3 g of sulfur element exhibited the best crystalline quality of kesterite phase with (112) preferential orientation. This result was confirmed by Raman spectroscopy. Surface morphology studied by scanning electron microscopy revealed that the post-sulfurization and especially the quantity of sulfur have a significant effect on the surface and roughness of thin films. According to the UV–Vis measurements, all films show high absorption in the visible region (~ 104 cm− 1) with a direct energy band gap ranging from 2.18 to 1.65 eV, which depends on the sulfur amount during the post-sulfurization. Finally, the electrical characterization by means of electrochemical impedance spectroscopy was carried out to analyze the capacitive nature of CZTS/Na2SO4 interface. This interface was modeled by an equivalent circuit approach. From the Mott–Schottky plot, the flat band potential and the acceptor density for CZTS thin films are determined. All the films demonstrated a p-type semiconductor character with a carrier density varying between 1016 and 1020 cm− 3.

Growth and dielectric characterizations of zinc stannate thin films deposited by RF magnetron sputtering

The microstructures and dielectric properties of zinc stannate (Zn2SnO4) thin films were investigated. Zn2SnO4 thin films were deposited on p-Si (1 1 0) substrate using the radio frequency magnetron sputtering with various Ar/(Ar + O2) ratios. The X-ray diffraction patterns of Zn2SnO4 thin films revealed that Zn2SnO4 is the main crystalline phase and is accompanied by small amounts of ZnSnO3 as second phase. The Zn2SnO4 thin films deposited at Ar/(Ar + O2) ratio of 1.0 showed a strong (3 1 1) preferred orientation. The grain size, thickness, and surface roughness of Zn2SnO4 thin films increased as the Ar/(Ar + O2) ratio increased. Dielectric constants () of 22-202 and loss factor of 0.22-0.41 of Zn2SnO4 thin films were measured at 1 MHz with Ar/(Ar + O2) ratio in the range of from 0.4 to 1.0. The leakage current density increased from to A/mm2 of Zn2SnO4 thin films applied at 0.1 MV/cm as Ar/(Ar + O2) ratio increased from 0.4 to 1.0.

3D Structure Revealing of Thin Films by Means of Focal Series

The aberration corrected transmission electron microscopy era inspires the development of new research methods. Due to small aberration many of HRTEM applications have become more precise and reliable. The research presented in this paper is devoted to developing a new method for revealing the 3D structure of thin films by focal series processing. We have obtained the sum of the Fourie power spectra in the sliding window of focal series images. Relative defocus value for the minimum of the power spectra is a target function depending on the thin film roughness. For amorphous CoNiP alloy films the new method shows roughness of up to 8 nm for site 65*65 nm in X, Y planes.

Effects of Cu doping on the structural and nanomechanical properties of ZnO thin films

The effects of Cu doping on the microstructures, surface morphological and nanomechanical properties of Cu-doped ZnO (CZO) thin films deposited on glass substrates by radio frequency magnetron sputtering method are investigated. The microstructural properties and surface morphological features of CZO thin films are characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The XRD results indicated that CZO thin films exhibited (002)-preferred orientation. From AFM observations, an increase in surface roughness of CZO thin films was observed when the Cu-doping concentration was increased from 2 at% up to 6 at%. Moreover, the nanoindentation tests performed with the continuous contact stiffness measurements (CSM) mode revealed that both the hardness and Young’s modulus of CZO thin films are increased with increasing the Cu-doping concentration, with the maximum value being obtained at 6 at%. Further increasing the Cu concentration up to 8 at% appeared to result in reduced microstructure texturing and nanomechanical performances, indicating that grain boundary effect might have played an important role.

CCTO thin film synthesis by radio frequency magnetron sputtering

In the present work CCTO thin film has successfully deposited on FTO substrate in a non-reactive (argon) atmosphere with frequency (RF) magnetron sputtering at 300 W. This work aims to determine the structural, morphological and optical properties of thin film using X-ray diffraction (XRD), atomic force microscopy (AFM) and Ultraviolet–visible spectroscopy (UV-Vis), respectively. The result shows that the nature of CCTO thin film is polycrystalline with cubic structure. XRD peaks confirmed the presence of CCTO phase with the crystal planes of (022), (013), (033), (024), and (224). The average crystallite size was 32 nm as measured by Willamson-Hall method. The surface roughness (Ra) and root mean square (RMS) of CCTO thin film were 26 nm and 33 nm, respectively. The maximum optical transmittance of CCTO thin film was more than 80% in the visible region (550-1000 nm) while calculated optical energy bandgaps was 3.2 eV.

A study on the optical, chemical and dielectric properties of PPCIN thin films derived from essential oil compounds using RF plasma polymerisation technique

Polymer-based nanostructured films were produced on various substrates using Radio Frequency (RF) plasma polymerization technique from Cinnamaldehyde monomer which is an organic compound. To fabricate polymer thin film, the pressure, the deposition time and RF power were set to 480 mTorr, 30 min and 15, 20 and 30 W, respectively. The effect of RF power on the optical, morphological and chemical properties of thin films were investigated. The optical, morphological and chemical properties were determined by UV–Vis spectroscopy, Atomic Force Microscopy (AFM) and FTIR spectroscopy, respectively. The average surface roughness of thin films was detected as 5.7 nm, 3.9 nm and 11.7 nm using AFM depending on the increase in RF power. Using FTIR spectroscopy, the chemical structure of the polymer thin films was compared with that of the monomer material, and it was found that the majority of the functional groups belonging to the monomers also appeared in the thin films. Optical band gap of thin films increased with RF power and these values were determined as 2.83 eV, 3.05 eV and 2.98 eV, respectively. The extinction coefficients and refractive indices of the thin films were measured at 500 nm between 0.00183–0.00522 and 2.40–2.78, respectively.

D-π-A-π-D type thiazolo[5,4-d]thiazole-core organic chromophore and graphene modified PEDOT:PSS buffer layer for efficient bulk heterojunction organic solar cells

A new thiazolo[5,4-d]thiazole-core organic chromophore with furan spacer (TP-FTzF-TP) was synthesized and PEDOT:PSS buffer layer was modified by graphene (Gr) for the efficient solution-processed bulk-heterojunction (BHJ) small molecule organic solar cells (SMOSCs). The introduction of furan as spacer in the thiazolo[5,4-d]thiazole-core based organic chromophore tuned the absorption and the electrochemical properties. The synthesized TP-FTzF-TP chromophore exhibited good optical parameters and a suitable HOMO/LUMO values of −5.33 eV/−3.15 eV. The synthesized organic chromophore with triphenylamine as a strong electron-donor and furan spacer promoted the charge transfer and charge extraction in fabricated SMOSCs. The modification of PEDOT:PSS by Gr considerably increased the roughness of thin film. The power conversion efficiency (PCE) of ∼3.63% was achieved by fabricated SMOSC device with ITO/Gr-PEDOT:PSS/TP-FTzF-TP:PC60BM (1:2, w/w)/Au architecture. It was found that the Gr-PEDOT:PSS as a buffer layer significantly enhanced PCE by two time factor as compared to the SMOSC device (PCE = ∼2.13%) with pristine PEDOT:PSS layer.