Effect of Pb:S molar ratio in precursor solution on the properties of lead sulphide thin films by ultrasonic spray pyrolysis

In this work, PbS thin films were deposited onto glass substrate at 225 °C by spraying precursor solution prepared with different molar ratio of lead acetate and thiourea as a source of Pb²⁺ and S^2- respectively in order to investigate the effect of Pb:S molar ratio in the precursor solution on the physical properties of PbS thin films. Structural investigations carried out by X-ray diffractometer have shown that all films have fcc cubic structure and the average crystal size increased from 11 nm to 25 nm with the increasing the thiourea ratio in the precursor solution. In order to analyze the surface morphology of PbS thin films, AFM and SEM images were taken and elemental analysis of the films was performed by EDS. Optical transmittance and absorption spectra show that all deposited films have fairly low transmittance and high absorbance in the visible region. Additionally, it was determined that optical band gap of the deposited films were varied between 1.18 eV and 1.37 eV. As a consequence of electrical investigations, it was seen that all films have p-type conductivity and electrical resistivity decreased by increasing thiourea molar ratio in the precursor solution. All examinations have revealed that the molar ratio of lead acetate and thiourea has a significant effect on the physical properties of PbS thin films.     

Effects of Sb,Zn doping on structural,electrical and optical properties of SnO2 thin films

Highly transparent, low resistive pure and Sb, Zn doped nanostructured SnO₂ thin films have been successfully prepared on glass substrates at 400° C by spray pyrolysis method. Structural, electrical and optical properties of pure and Sb, Zn doped SnO₂ thin films are studied in detail. Powder X-ray diffraction confirms the phase purity, increase in crystallinity, size of the grains (90–45 nm), polycrystalline nature and tetragonal rutile structure of thin films. The scanning electron microscopy reveals the continuous change in surface morphology of thin films and size of the grains decrease due to Sb, Zn doping in to SnO₂. The optical transmission spectra of SnO₂ films as a function of wavelength confirm that the optical transmission increases with Sb, Zn doping remarkably. The optical band gap of undoped film is found to be 4.27 eV and decreases with Sb, Zn doping to 4.19 eV, 4.07 eV respectively. The results of electrical measurements indicate that the sheet resistance of the deposited films improves with Sb, Zn doping. The Hall measurements confirm that the films are degenerate n-type semiconductors.     

Effect of doping concentration on the properties of bismuth doped tin sulfide thin films prepared by spray pyrolysis

Bismuth doped tin sulfide (SnS:Bi) thin films were deposited onto glass substrates by the spray pyrolysis technique at the substrate temperature of 350 °C. The effect of doping concentration [Bi/Sn] on their structural, optical and electrical properties was investigated as a function of bismuth doping between 0 and 8 at%. The XRD results showed that the films were polycrystalline SnS with orthorhombic structure and the crystallites in the films were oriented along (111) direction. Atomic force microscopy revealed that the particle size and surface roughness of the films increased due to Bi-doping. Optical analysis exhibited the band gap value of 1.40 eV for SnS:Bi (6 at%) which was lower than the band gap value for 0 at% of Bi (1.60 eV). The film has low resistivity of 4.788×10⁻¹ Ω-cm and higher carrier concentration of 3.625×10¹⁸ cm⁻³ was obtained at a doping ratio of 6 at%.     

Optical,morphological and electrical studies of Zn:PbS thin films

Structural, electrical, and optical properties of undoped and Zn doped lead sulfide (PbS) thin films are benign reported in this paper. The subjected films were grown on glass substrates at 25 °C by a chemical bath deposition (CBD) method. The concentration of Zn in the deposition bath represented by the ratio [Zn²⁺]/[Pb²⁺] was varied from 0% to 5%. It was found that the film׳s grains decreased in size with increasing Zn content in the film. XRD data showed the polycrystalline nature of the film its crystal orientation peak intensities decreased with higher doping concentration of Zn. Atomic force microscopy (AFM) measurements revealed that the surface roughness of the films decreased due to zinc doping as well. However, with increasing of the dopant concentration from 0% to 5%, the average transmittance of the films varied over the range of 35–75%. The estimated optical band (E_g) gaps of undoped and Zn doped PbS thin films were in the range of 0.72–1.46 eV. Hall Effect measurements electrical resistivity, carrier concentration and Hall mobility have been determined for the titled film as functions on the Zn content within the film׳s textures. The overall result of this work suggested that the Zn:PbS film is a good candidate as an absorber layer in the modern solar cell devices.     

Influence of Mn doping on structural,optical and electrical properties of CdO thin films prepared by cost effective spray pyrolysis method

Transparent and conducting cadmium oxide (CdO) and manganese doped CdO (Mn: CdO) thin films were deposited using a low cost spray pyrolysis method on the glass substrate at 300 °C. For Mn doping, various concentrations of manganese acetate (1–3 wt%) was used in the spraying precursor solution. The structural, electrical and optical properties of CdO and Mn: CdO films were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), UV–vis and Hall measurement. X-ray diffraction study reveals that the CdO and Mn: CdO films are possessing cubic crystal structures. SEM and AFM studies reveal that the grain size and roughness of the films are increased with increasing Mn doping concentration. Optical transmittance spectra of the CdO film decreases with increasing doping concentration of manganese. The optical band gap of the films decreases from 2.42 eV to 2.08 eV with increasing concentration of manganese. A minimum resistivity of 1.11×10⁻³ Ω cm and maximum mobility of 20.77 cm² V⁻¹ s⁻¹ is achieved for 1 wt% of manganese doping.     

The effect of introducing Al ions in cationic deposition bath on as-prepared PbS thin film through SILAR deposition method

Undoped and Al doped lead sulfide (PbS) thin films were grown on soda lime glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. Al content in aqueous cationic solution was varied by adding 0.5–2% of aluminum nitrate in step of 0.5. The characterization of the film was carried out using X-ray diffraction, scanning electron microscopy, and optical and electrical measurement techniques. X-ray diffraction analysis revealed that both the undoped and doped films were polycrystalline and exhibited galena type cubic structure with average crystallite size in the range of 15.5–30.9 nm. The compositional analysis results indicated that Pb, S and Al were present in the samples. Optical studies revealed prominent blue-shift in the absorption edge of as-deposited samples upon doping as compared to that of bulk PbS and this shift was due to a quantum confinement effect. The room temperature conductivity of the PbS thin films was in the range of 1.343×10⁻⁷–1.009×10⁻⁶ (Ω cm)⁻¹for doped samples and 5.172×10⁻⁸ for undoped PbS thin film sample. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and microstrain. The estimated lattice parameter, grain size, optical band gaps and electrical properties were correlated with Al concentration in the cationic solution.     

Behavior of chemically deposited PbS thin films subjected to two different routes of post deposition annealing

Lead sulfide (PbS) thin films were prepared on soda lime glass substrates at room temperature by Chemical Bath Deposition (CBD) technique. This paper reports a comparative study of characteristic properties of as-prepared PbS thin films after thermal treatment through two different routes. Studies were carried out for as-prepared as well as rapidly and gradually annealed samples at 100, 200 and 300 °C. The characterizations of the films were carried out using X-ray diffraction, scanning electron microscopy and optical measurement techniques. The structural studies confirmed the polycrystalline nature and the cubic structure of the films. As-deposited films partly transformed to Pb₂O₃ when gradually annealed to 300 °C. The presence of nano crystallites was revealed by structural and optical absorption measurements. The values of average crystallite size were found to be in the range 18–20 nm. The variation in the microstructure, thickness, grain size, micro strain and optical band gap on two types of annealing were compared and analyzed. Data showed that post deposition parameters and thermal treatment strongly influence the optical properties of PbS films. Optical band gap of the film gets modified remarkably on annealing. Direct band gap energy values for rapidly and gradually annealed samples varied in the range of 1.68–2.01 eV and 1.68–2.12 eV respectively. Thus we were succeeded in tailoring direct band gap energies by post deposition annealing method.     

Structural,morphological, electrical and optical studies of Cr doped SnO2 thin films deposited by the spray pyrolysis technique

Tin oxide (SnO₂) and chromium (Cr) doped tin oxide (Cr:SnO₂) thin films were deposited on the preheated glass substrates at 673 K by spray pyrolysis. Concentration of Cr was varied in the solution by adding chromium (III) chloride hexahydrate from 0 to 3 at%. The effect of Cr doping on the structural, electrical and optical properties of tin oxide films is reported. X-ray diffraction pattern confirms the tetragonal crystal structure for undoped and Cr doped tin oxide films. Scanning electron microscopic photographs show the modification of surface morphology of tin oxide film due to varying concentration of Cr. X-ray photoelectron spectra of Cr:SnO₂ (3 at%) thin film revealed the presence of carbon, tin, oxygen, and chromium. Carrier concentration and mobility of the SnO₂ films decrease with increasing concentration of Cr and 0.5 at% Cr doped tin oxide film acquires a mobility of 70 cm²/V s. Average optical transmittance in the 550–850 nm range varies from 38% to 47% with varying Cr concentration in the solution.     

Effect of annealing temperature on optical and electrical properties of lead sulfide thin films

Lead sulfide (PbS) thin films with 150 nm thickness were prepared onto ultra-clean quartz substrate by the RF-sputtering deposition method. Deposited thin films of PbS were annealed at different temperatures 100 °C, 150 °C, 200 °C, 250 °C and 300 °C. X-ray diffraction pattern of thin films revealed that thin films crystallized at 150 °C. Crystalline thin films had cubic phase and rock salt structure. The average crystallite size of crystalline thin films was 22 nm, 28 nm and 29 nm for 150 °C, 200 °C and 250 °C respectively. From 150 °C to 250 °C increase in annealing temperature leads to increase in crystallite arrangement. FESEM images of thin films revealed that crystallite arrangement improved by increasing annealing temperature up to 250 °C. Increase in DC electrical conductivity by increasing temperature confirmed the semiconductor nature of crystalline thin films. Increase in dark current by increasing annealing temperature showed the effect of crystallite arrangement on carrier transport. Photosensitivity decreased by increasing annealing temperature for crystalline thin films that it was explained at the base of thermal quenching of photoconductivity and adsorption of oxygen at the surface of thin films that leads to the formation of PbO at higher temperatures.     

Influence of magnesium doping on the structural and optical properties of tin (II) oxide thin films deposited by electron beam evaporation

Single-phase polycrystalline magnesium-doped tin oxide (Mg_xSn_1?xO; x=0, 0.04, and 0.08) thin films were deposited by electron beam evaporation on the glass substrate. X-ray diffraction analysis showed that the peaks intensity of the polycrystalline α-SnO thin films increased along with the increasing Mg content. The crystallite size calculated from X-ray diffraction data decreased by increasing the Mg doping concentration, which was also confirmed by atomic force microscopy. The stoichiometry and thickness of the thin films were determined by Rutherford backscattering spectroscopy. An increase in both the optical transmission (57–95%) and band gap (2.5–2.82 eV) of the Mg_xSn_1?xO thin films were observed which were investigated by UV–vis spectroscopy. Photoluminescence of Mg_xSn_1?xO thin films revealed that there were two extra peaks at 482 nm and 550 nm due to the crystal defects introduced by the Mg doping and these peaks become weaker and shifted to longer wavelength by increasing the Mg doping concentration.     

Deposition and characterization of pure and Cd doped SnO2 thin films by the nebulizer spray pyrolysis (NSP) technique

Pure and cadmium doped tin oxide thin films were deposited on glass substrates from aqueous solution of cadmium acetate, tin (IV) chloride and sodium hydroxide by the nebulizer spray pyrolysis (NSP) technique. X-ray diffraction reveals that all films have tetragonal crystalline structure with preferential orientation along (200) plane. On application of the Scherrer formula, it is found that the maximum size of grains is 67 nm. Scanning electron microscopy shows that the grains are of rod and spherical in shape. Energy dispersive X-ray analysis reveals the average ratio of the atomic percentage of pure and Cd doped SnO₂ films. The electrical resistivity is found to be 10² Ω cm at higher temperature (170 °C) and 10³ Ω cm at lower temperature (30 °C). Optical band gap energy was determined from transmittance and absorbance data obtained from UV–vis spectra. Optical studies reveal that the band gap energy decreases from 3.90 eV to 3.52 eV due to the addition of Cd as dopant with different concentrations.     

Deposition of morphology-tailored PbS thin films by surfactant-enhanced aerosol assisted chemical vapor deposition

In this work, we report the results of deposition of PbS thin films using single molecular precursor, bis(O-isobutylxanthato)lead(II), in the presence of additives namely: sodium dodecyl sulfate (SDS), Tween and Triton x-100, via aerosol assisted chemical vapor deposition (AACVD). The as-deposited PbS thin films are highly crystalline and exhibited superior adhesion to glass substrates. Powder X-ray diffraction (XRD) analysis confirmed the formation of pure cubic phase of PbS. Thin films deposited using 0.4 mM Triton X-100 as additive resulted in wire like structures while 0.8 mM Triton X-100 deposited thin films comprised of predominantly shoe shaped structures. Further, increase in concentration (1.2 mM) of Triton X-100 deposited films having rod like morphology. The scanning electron microscopy (SEM) confirmed that in the presence of SDS, thin films consist of spherical shaped crystallites. Energy dispersive X-ray spectroscopy (EDX) and X-ray photon electron microscopy (XPS) of as-deposited PbS thin films was used to study chemical composition of thin films.     

Influence of Cu doping on physical properties of sol-gel processed SnS thin films

Copper-doped tin sulfide thin films (Cu-SnS) with different Cu doping concentrations were prepared by using the spin coating technique and their structural, electrical, and optical properties were studied. All the prepared films were polycrystalline and exhibited diffraction peaks corresponding to orthorhombic SnS with the preferred (111) orientation. The XRD spectra revealed improvement in the preferential orientation and crystalline quality with up to 4% Cu doping concentration, whereas Cu doping concentrations above 4% deteriorate the preferential orientation and crystalline quality. It has been observed that upon Cu doping the band gap decreased significantly from 1.46 eV (pure SnS) to 1.37 eV (4% of Cu-doped SnS). Hall measurements revealed the p-type semiconducting nature of the SnS thin films. The observations revealed that doping of SnS with Cu causes a noticeable drop in the room-temperature resistivity value from 10⁵ Ω-cm for pure SnS to 10³ Ω-cm for 4% Cu-doped SnS.     

Structural,surface morphology and optical properties of sputter-coated CaCu3Ti4O12 thin film: Influence of RF magnetron sputtering power

This study focusses on the investigation of RF power variations (100–300 W) effects on structural, morphological and optical properties of CaCu₃Ti₄O₁₂ thin film deposited on ITO/glass substrate in a non-reactive atmosphere (Ar). The increase of RF power from 100 W to 300 W led to evolution of (112), (022), (033), and (224) of CCTO XRD peaks. The results indicated that all the films were polycrystalline nature with cubic structure. The crystallite size increased from 20 nm to 25 nm with increasing RF power. FESEM revealed that the films deposited were uniform, porous with granular form, while the grain size increased from 30 to 50 nm. AFM analysis confirmed the increment in surface roughness from 1.6 to 2.3 nm with increasing film grain size. Besides, optical transmittance values decreased to minimum 70% with increasing RF power while optical energy bandgap increased from 3.20 eV to 3.44 eV. Therefore, favorable CCTO thin film properties can be possibly obtained for certain application by controlling RF magnetron sputtering power.     

Investigations on the structural and optical properties of Li,N and (Li,N) co-doped ZnO thin films prepared by sol–gel technique

Pure and doped zinc oxide thin films have been deposited on sapphire substrates by using the sol–gel method and spin coating technique. The X-ray diffraction pattern showed that the deposited films exhibit hexagonal zinc oxide structure. Room temperature photoluminescence measurements show the presence of two emission bands. The predominant near band edge ultraviolet emission is at 3.28 eV and a suppressed broad band of deep level emission in the range of 2.1–2.5 eV. The incorporation of nitrogen is indicative of p-type behavior as observed from X-ray photoelectron spectrum of nitrogen in the doped samples. The p-type conduction of Li, N:ZnO may be attributed to the formation of a LiZn–N complex acceptor.     

Microstructure and electrical properties of nitrogen doped 3C–SiC thin films deposited using methyltrichlorosilane

The growth, microstructure and electrical properties of in-situ nitrogen doped 3C–SiC (111) thin films for sensor applications are presented in this paper. These thin films are deposited at a pressure of 2.5 mbar and temperature of 1040 °C on thermally oxidized Si (100) substrates from methyltrichlorosilane (MTS) precursor using a hot wall vertical low pressure chemical vapor deposition (LPCVD) reactor. Ammonia (NH₃) is used as the nitrogen doping gas. The sensor response depends on chemical composition, structure, morphology and operating temperature. The above properties are investigated for all in situ nitrogen doped (0, 9, 17 and 30 at% of nitrogen) 3C–SiC thin films using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and four probe method. The XRD patterns of the 3C–SiC thin films show a decrease in the crystallinity and intensity of the peak with increase in dopant concentration from 0 to 17 at%. AFM investigations show an improvement in the grain size of the nitrogen doped 3C–SiC thin films with increase in nitrogen concentration from 0 to 17 at%. The sheet resistance of nitrogen doped 3C–SiC thin films is measured by the four probe technique and it is found to decrease with increase in temperature in the range of 40–550 °C. The resistivity and average temperature coefficient of resistance (TCR) of doped 3C–SiC thin film deposited with 17 at% of nitrogen concentration are found to be 0.14 Ω cm and −103 ppm/°C, respectively and this can be used as a sensing material for high temperature applications.     

Bias voltage dependence properties of Nb-doped indium tin oxide thin films by RF magnetron sputtering at room temperature

Niobium doped indium tin oxide (ITO:Nb) thin films were fabricated on glass substrates by RF magnetron sputtering from one piece of ceramic target material at room temperature. The bias voltage dependence of properties of the ITO:Nb films were investigated by adjusting the bias voltage. Structural, electrical and optical properties of the films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible spectroscopy, and electrical measurements. XRD patterns showed a change in the preferential orientations of polycrystalline crystalline structure from (222) to (400) crystal plane with the increase of negative bias voltage. AFM analysis revealed that the smooth film was obtained at a negative bias voltage of -120 V. The root mean square (RMS) roughness and the average roughness are 1.37 nm and 1.77 nm, respectively. The films with the lowest resistivity as low as 1.45×10⁻⁴ Ω cm and transmittance over 88% have been obtained at a negative bias voltage of −120 V. Band gap energy of the films, depends on substrate temperature, varied from 3.56 eV to 3.62 eV.     

Effect of pH on the properties of electrochemically prepared ZnO thin films

Zinc Oxide (ZnO) thin films have been electrochemically deposited on fluorine doped tin oxide (FTO) coated glass substrates from an aqueous electrolyte. Deposition potential −0.96 V was optimized by cyclic voltammetry experiment for slow scan rate 5 mV/s with moderate agitation of electrolyte. The effect of pH on the electrodeposition of ZnO is studied by cyclic voltammetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), optical spectroscopy and photoelectrochemical I-t transient characteristics. It is revealed that the pH of the electrolyte has significant influence on the surface morphology and structural properties. Highly crystalline ZnO layers with hexagonal crystal structure deposited for all pH of the solutions. A systematic shift observed in the reflections (002) and (101) is correlated with an effective tensile strain developed in the crystal lattice. A remarkable improvement in the crystallinity was noticed in the as-deposited ZnO samples with increasing pH and upon heat treatment. Optical direct band gap ~ 3.26–3.33 eV and transmittance ~70 −80% was measured by optical spectroscopy. PL measurement showed the band edge emission at 375–382 nm and a visible light emission at 410–550 nm. The intensities of emission peaks are found to be affected by the pH of bath. The compact, densely packed and well adherent thin films of ZnO electrodeposited in zinc nitrate bath for pH 2.0, 3.5 and 6.0. The surface morphology has been changed from granular to disc shaped and finally a large hexagonal sheets were obtained with an increase in the pH of bath. Nearly stoichiometric ZnO thin films are electrodeposited at −0.96 V versus Ag/AgCl reference electrode for pH 6.0. The photoelectrochemical (PEC) measurement (I-t transient curve) shows the enhancement in photocurrent with increasing the pH of zinc nitrate solution. After heat treatment the photocurrent is increased by 54%, 98% and 130% in the samples deposited from 2.0, 3.5 and 6.0 pH of the bath. I-V measurements were further confirmed the current enhancement in all samples after heat treatment.     

Effect of Bi doping on structural,morphological, optical and ethanol vapor response properties of SnO2 nanoparticles

The gas sensing behavior of thick films of Bi doped SnO₂ has been investigated towards ethanol vapor. The screen printing technique was used to prepare the thick films. The films were sintered at 650 °C for 2 h. The structural, surface morphological, optical and gas sensing properties of undoped and Bi doped SnO₂ thick films have been studied. X-ray diffraction and Raman spectroscopy confirmed that the films consisted exclusively of tetragonal tin oxide, without any impurity phases. FE-SEM studies revealed the formation of highly porous microstructure with grain size in few tens of nanometers. From the optical studies, the band gap was found to be decreased with bismuth doping (3.96 eV for undoped, 3.83 eV, 3.71 eV and 3.6 eV for 1 mol%, 2 mol% and 3 mol% Bi, respectively). The 3 mol % Bi doped SnO₂ thick films exhibited the highest sensitivity to 100 ppm of ethanol vapor at 300 °C. The effect of microstructure on sensitivity, response time and recovery time of the sensor was studied and discussed.     

Effect of Al dopant concentration on structural,optical and photoconducting properties in nanostructured zinc oxide thin films

Thin films of undoped and doped ZnO, with different Al concentrations (1–5 wt%) were deposited onto glass substrates, by the sol–gel spin coating method. Grazing incidence X-ray diffraction (GIXRD) studies confirmed the nature of films as poly-crystalline, with typical hexagonal wurtzite structure. The films showed variation in crystallite size and change in relative intensities, upon different Al doping concentrations. The surface morphology of the films examined using FE-SEM, showed the grain size becoming smaller upon Al doping. The influence of Al with different concentrations, onto ZnO on the optical absorption and transmittance was studied using UV–Vis–NIR spectrophotometer in the wavelength range 300–2500 nm. The UV absorption shifted towards shorter wavelength upon Al doping. The average transmittance in the visible region increased for Al doped films up to 1–2 wt% and decreased for other concentration. The dark and photo conductivity measurements of the films indicated increase in the current values upon doping up to 1–2 wt% of Al and decreased for further concentrations. The rise and decay time measured from the photoresponse study, indicate larger values of rise time for the doped films compared to undoped ZnO. However, the film with 1–2 wt% doping of Al showed better response within the doping concentration. The thermal activation energy obtained from temperature-dependant conductivity showed decrease in the value upon Al doping up to 2 wt% and increased beyond this concentration in the temperature range 300–400 K.