Electrical Properties Of Thin Films Research Articles

Mechanochemical Synthesis of YFeO3 Nanoparticles: Optical and Electrical Properties of Thin Films

Nanoparticles (NPs) of orthorhombic YFeO3, has been successfully synthesized via an uncomplicated mechanochemical method from yttrium and iron chloride salts in a basic medium. The YFeO3 NPs were characterized by micro-Raman and Fourier-transform infrared spectroscopy. Their crystalline structure and average diameter of 30 nm was determined from X-ray powder diffraction pattern and by transmission electron microscopy images. Thin films (TF) of these NPs in polystyrene were prepared by spin coating in order to study their electrical and optical properties, as well as to verify their possible application in the manufacture of optoelectronic devices. UV–visible diffuse reflectance was performed for YFeO3 NPs and for YFeO3 TF and optical band gaps of 2.38 and 3.7 eV, respectively, were estimated from optical absorption measurements. The electrical conductivity of the YFeO3 TF was evaluated in a glass/ITO/YFeO 3 TF/Ag device. At low voltages, electric current in the forward direction was found to obey an ohmic I–V relationship; at higher voltages, the behavior of the film in the device is defined by a Space Charge Limited Current model and, at around 1 V, current saturation. These results suggest the possibility of using YFeO3 TF in the production of dielectric layers in electronic or optoelectronic devices.

Structural, Optical and Electrical Properties of ITO Thin Films

Transparent and conductive thin films of indium tin oxide were fabricated on glass substrates by the thermal evaporation technique. Tin doped indium ingots with low tin content were evaporated in vacuum (1.33 × 10−7 kpa) followed by an oxidation for 15 min in the atmosphere in the temperature range of 600–700°C. The structure and phase purity, surface morphology, optical and electrical properties of thin films were studied by x-ray diffractometry and Raman spectroscopy, scanning electron microcopy and atomic force microscopy, UV–visible spectrometry and Hall measurements in the van der Pauw configuration. The x-ray diffraction study showed the formation of the cubical phase of polycrystalline thin films. The morphological analysis showed the formation of ginger like structures and the energy dispersive x-ray spectrum confirmed the presence of indium (In), tin (Sn) and oxygen (O) elements. Hall measurements confirmed n-type conductivity of films with low electrical resistivity (ρ) ∼ 10−3 Ω cm and high carrier concentration (n) ∼ 1020 cm−3. For prevalent scattering mechanisms in the films, experimental data was analyzed by calculating a mean free path (L) using a highly degenerate electron gas model. Furthermore, to investigate the performance of the deposited films as a transparent conductive material, the optical figure of merit was obtained for all the samples.

The effect of processing solvent dependent film aggregation on the photovoltaic performance of squaraine:PC71BM bulk heterojunction solar cells

In this work, we systemically investigated the processing solvent-dependent aggregation behavior of a squaraine dye, 2,4-bis[4-(N,N-dibutylamino)-2,6- dihydroxyphenyl] squaraine (DBSQ), in a DBSQ: [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) blend film, as well as the aggregation effect on the photovoltaic performance of DBSQ:PC71BM bulk heterojunctions (BHJs). Our finding shows that the aggregation behavior of DBSQ dye in the blend film can be controlled via the proper selection of the processing solvents. For a J-aggregate (head-to-tail molecule alignment) DBSQ:PC71BM active layer based BHJ cells, a power conversion efficiency (PCE) of over 5% can be obtained, which is 75% higher than that of the H-aggregate (parallel molecule packing) active layer based BHJ cells. Our results indicate that the processing solvent controlled J-aggregation formation shall be considered as effective approach to tune the optical and electrical properties of thin films for high-performance BHJ solar cells.

The Changes of Structure and Electrical Properties of Thin Films During Long-Term Aging

The changes of surface structure and electrical properties of crystalline thin films of ternary compounds (La, Y, Sc)-(Ni, Fe)-Ge with metal content not more than 50 at. percent, which are obtained by vacuum deposition, are investigated. The directions of growth defects of films in aging over 20 years shown also as the influence of aging on the electrical properties of the condensates are analyzed.

Electrical transport characterization of Al and Sn doped Mg2Si thin films

Thin-film Mg2Si was deposited using radio frequency (RF) magnetron sputtering. Al and Sn were incorporated as n-type dopants using co-sputtering to tune the thin-film electrical properties. X-ray diffraction (XRD) analysis confirmed that the deposited films are polycrystalline Mg2Si. The Sn and Al doping concentrations were measured using Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray spectroscopy (EDS). The charge carrier concentration and the charge carrier type of the Mg2Si films were measured using a Hall bar structure. Hall measurements show that as the doping concentration increases, the carrier concentration of the Al-doped films increases, whereas the carrier concentration of the Sn-doped films decreases. Combined with the resistivity measurements, the mobility of the Al-doped Mg2Si films is found to decrease with increasing doping concentration, whereas the mobility of the Sn-doped Mg2Si films is found to increase.

On the structural, morphological and electrical properties of tantalum oxy nitride thin films by varying oxygen percentage in reactive gases plasma

Tantalum oxy nitride (Ta-ON) thin films possess unique properties due to combined beneficial aspects of tantalum nitride and tantalum oxide. In the present work, Ta-ON thin films are synthesized using energetic ions and electrons beams emanated from the hot and decaying plasma in dense plasma focus (DPF) device. Oxygen percentage in the reactive gas admixture [O/(O+N)]% is varied from 10 to 60 for thin film synthesis. Influence of oxygen percentage on structural, morphological, compositional and electrical properties of thin films is also analyzed. Increase of oxygen percentage in the gas admixture (upto 40%) resulted in transformation of thin film from tantalum nitride to tantalum oxy nitride; however; higher oxygen percentages (≥ 50%) caused amorphization in synthesized thin film. Morphological analysis revealed that pure nitrogen environment yields the granular structure of film in nano-meter range whereas escalation of grains is observed with the increase in oxygen percentage. Cross sectional SEM showed better film growth rate at lower oxygen percentages. Compositional profiles exhibited improvement of oxygen content in thin film by increasing oxygen percentage in the admixture. The electrical resistivity of films shifted from conducting (for 0% oxygen) to semiconducting-insulating (for 60% oxygen) material range for maximum oxygen percentage.

Tuning the Curie temperature of epitaxial Nd0.6Sr0.4MnO3 thin films

NdxSr1−xMnO3 (0.2≤x≤0.5) systems are widely studied in magnetism, popular for high colossal magnetoresistance and are ferromagnetic oxides with TC ranging from 200K to 300K. Recently, many of such compounds are re-visited for exploring the correlation of spin, charge and lattice degrees of freedom. Although, manganite thin films are the ideal candidates for studying the electron-correlation effects, the puzzle of obtaining a high quality epitaxial thin films of NdxSr1−xMnO3 are still unsolved contrary to its sister compound LaxSr1−xMnO3. Hence, in this study, we demonstrate the growth of best quality of Nd0.6Sr0.4MnO3 (NSMO) epitaxial thin films. This is evident from the TC and a sharp insulator-to-metal transition (IMT) coinciding at as high as ∼255K against the bulk TC (∼270K). It is the highest reported TC in Nd0.6Sr0.4MnO3 thin films to date. Moreover, as-deposited films with in situ oxygen annealing are not enough to relax the lattice of NSMO films due to the significant Jahn-Teller distortion in the film. With ex situ annealing processes alongside the various deposition and in situ annealing conditions, we have extensively studied the growth of epitaxial NSMO thin films on LaAlO3 (001) and SrTiO3 (001) to investigate the evolution of lattice and its one-to-one correspondence with the magnetism and the electrical properties of thin films. Accordingly, the enhanced magnetization, reduced resistivity and the higher TC and IMT of the NSMO films obtained from our extensive growth analysis looks promising for the future applications across the TC and IMT.

Electronic excitation induced modifications of nanostructured Ni-Ti shape memory alloy thin films

In the present work, the effects of 120 MeV Au ion irradiation at different fluences ranging from 1×10 12 to 3×10 13 ions/cm 2 on structural and electrical properties of thin films of Nickel-titanium (Ni-Ti) shape memory alloys (SMAs) grown on Si substrate using DC magnetron co-sputtering is studied. The surface morphology, crystallization and phase transformation behaviour of these films were investigated using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Four-terminal resistivity measurement method. XRD pattern reveals that both the phases-martensite as well as austenite exist in the pristine film. Resistivity measurements revealed a two way transformation from cubic to rhombohedral and from rhombohedral to monoclinic phase in pristine film and decrease in its transformation temperature with increased fluence. At higher fluences 5×10 12 and 1×10 13 ions/cm 2 , films showed non-metallic behaviour which could be due to the disorder occurring in these films due to ion impact and precipitate formation. The elemental composition of pristine film is determined by Rutherford backscattering spectroscopy.

Postdeposition annealing on RF-sputtered SrTiO3 thin films

Understanding of structural, optical, and electrical properties of thin films are very important for a reliable device performance. In the present work, the effect of postdeposition annealing on stoichiometric SrTiO3 (STO) thin films grown by radio frequency magnetron sputtering at room temperature on p-type Si (100) and quartz substrates were studied. Highly transparent and well adhered thin films were obtained in visible and near infrared regions. As-deposited films were amorphous, while nanocrystalline and polycrystalline phases of the STO thin films formed as a function of annealing temperature. Films annealed at 300 °C showed nanocrystallinity with some amorphous phase. Crystallization started after 15 min annealing at 700 °C, and further improved for films annealed at 800 °C. However, crystallinity reduced for films which were annealed at 900 °C. The optical and electrical properties of STO thin films affected by postdeposition annealing at 800 °C: Eg values decreased from 4.50 to 4.18 eV, n(λ) values (at 550 nm) increased from 1.81 to 2.16. The surface roughness increased with the annealing temperature due to the increased crystallite size, densification and following void formation which can be seen from the scanning electron microscopy images. The highest dielectric constants (46 at 100 kHz) observed for films annealed at 800 °C; however, it was lower for 300 °C annealed (25 at 100 kHz) and as-deposited (7 at 100 kHz) STO films having ∼80 nm thickness.

Influence of Ag concentration on the structure, optical and electrical properties of SnS2:Ag thin films prepared by spray pyrolysis deposition

Ag-doped tin-sulfide thin films were deposited with in spray pyrolysis method at T = 425 °C on soda lime glass substrates. The effects of Ag doping were investigated on the structural, optical, and electrical properties of thin films. Double deionized water was used as a precursor solution in which tin chloride (SnCl45H2O) and thiourea (CS(NH3)2) in addition to silver acetate (AgC2H3O2) were dissolved. All in all resulted to preparation of SnS2:Ag thin films with $$\frac{{\left[ {\text{Ag}} \right]}}{{\left[ {\text{Sn}} \right]}}\% = 0, \,1, \,2, \,3\, {\text{and}} \,4\,{\text{at}}.\%$$ . The (001) plane is the preferred orientation of the SnS2 phase which is analyzed by X-ray diffraction (XRD). The intensity of mentioned peak has an increasing trend, generally, with increasing Ag doping concentration. Thin films have spherical grains as is shown in SEM images. Increasing doping concentration from 1 to 4%, causes decrease in: single-crystal grains from 14.68 to 6.31 nm, optical band gap from 2.75 to 2.62 eV, carrier concentration from 3.11 × 1017 to 2.58 × 1017 cm−3, and Hall mobility from 1.81 to 0.13 cm2/v s, as well as increase in: average grain size, generally, from 70 to 79 nm and electrical resistance from 11.11 to 181.26 Ω cm, respectively. The majority carriers are electrons for these films as is concluded from Hall Effect measurements.

Study of electrical properties of hafnium oxide thin film based metal–insulator–metal capacitors: pre and post metallic annealing

Metal–insulator–metal (MIM) capacitors having hafnium oxide (HfO2) high-κ dielectric thin film were fabricated and subsequently studied for their electrical and micro-structural properties. The MIM capacitors were found to possess low leakage current density of about 2.7 × 10−9 A/cm2 at −1 V, high capacitance density of about 18.1 fF/μm2 at 0 V, 1 MHz and improved quadratic voltage coefficient of capacitance (VCC) of about 120 ppm/V2 at 1 MHz. The electrical properties of MIM capacitors are found to be governed by Frenkel–Poole mechanism at low and intermediate fields ( 1500 kV/cm). The dielectric thin films have amorphous structure which has been correlated with the electrical properties of MIM capacitors. The HfO2 thin film possess good micro-structural properties in term of low roughness, which is in agreement with the obtained electrical properties of thin film based MIM capacitors. Further, post metallic annealing of MIM capacitors results in decrease in leakage current density to ~5.1 × 10−10 A/cm2 at −1 V, increase in capacitance density to ~23.1 fF/μm2 at 0 V, 1 MHz and improvement in quadratic VCC to reach a value of ~95 ppm/V2 at 1 MHz. The electrical characteristics of as-fabricated and annealed MIM capacitors are in accordance with the International Technology Roadmap for Semiconductor 2013 guidelines. The obtained electrical properties suggest the possible use of MIM capacitors in analog/mixed-signal applications.

Infrared, transient thermal, and electrical properties of silver nanowire thin films for transparent heaters and energy‐efficient coatings

In this study, we investigate the infrared and electrical properties as well as the thermal response of transparent silver nanowire (AgNW) based thin‐film heaters, when subjected to Joule heating. Controlling the number of layers and hence the deposition time, our spray‐coating technique allows to modulate the thermal and electrical properties of the thin films in a precise manner. In addition, this technique enables the fabrication of homogeneous and large‐area heaters, which, in terms of their electro‐optical properties, nicely compare to the performances of state‐of‐the‐art AgNW transparent electrodes. The thermal response and the electrical properties are accurately reproduced by a purposely developed physical model, which shows that the temperature dependence of the AgNW film resistance is lowered by a factor of 2 compared to bulk silver, independently of the number of deposited layers. Compared to uncoated glass, the emissivity decreases by 58% at a coverage rate of 58%. At the same time, the AgNW film can sustain a transparency as high as 81.3%. Therefore, AgNW‐based thin films can be used as a low‐emissivity coating, for e.g., energy‐efficient window glazing applications. Finally, we accurately determine the fragmentation temperature of AgNWs, which sets the ultimate limitation of use for heating applications.

Study of optical and electrical properties of thin films of the conducting comb-like graft copolymer of polymethylsiloxane with poly(3-hexyltiophene) and poly(ethylene) glycol side chains for low temperature NO2 sensing

This work presents an investigation on graft comb copolymer of polymethylsiloxane (PMS) with poly(3-hexyltiophene) (P3HT) and poly(ethylene) glycol as functional side groups. This segmented copolymer was investigated as a NO2 gas sensing material. Gas sensing, optical and electrical properties of thin films of graft polymers and clean P3HTs (regioregular and regiorandom) are tested and compared. The thin films of investigated materials obtained by spin coating method on interdigital transducers and surface plasmon resonance (SPR) sensor structure are characterized by using atomic force microscopy method and Raman spectroscopy. High changes of resistance and SPR signal caused by action of NO2 in the concentration of ppm range were observed. It showed that such graft polymers are promising materials for resistance and optical gas sensors operating at low temperatures. Obtained results showed that resistance and sensitivity of graft polymers depend on the content of P3HT and PMS backbone chain length. An optical SPR NO2 gas sensor and resistance NO2 sensor based on graft polymer thin films display a very fast response time and a fast regeneration time at low temperature (50°C) in a dry gaseous environment. Resistance sensor investigation showed that the sensitivity of graft polymers to 5ppm of NO2 can be about 20 times higher than in the case of clean P3HTs.

Annealing behavior of ferroelectric Si-doped HfO2 thin films

Rapid thermal annealing of 10nm thick Si-doped HfO2 thin films was performed to study the influence of isochronal and isothermal anneals on the ferroelectric and electrical properties of thin film metal-ferroelectric-metal capacitors. The anneal temperature and time dependence of the ferroelectric Si-doped HfO2 thin films was investigated by applying 700°C–900°C rapid thermal anneals for 5s–60s durations. An antiferroelectric-like to ferroelectric transition with increasing anneal temperature is observed in the Si-doped HfO2 thin films. The electrical properties of Si-doped HfO2 thin films exhibit a strong temperature dependence and a significant time dependence for the temporal range studied in this work. The breakdown field in the ferroelectric HfO2 thin films ranges from 3.8–5.3MV/cm depending on the anneal temperature and atomic layer deposition cycle ratio. The remanent polarization, breakdown field, and leakage current is discussed in the context of the Si-doping, anneal temperature, and anneal time. Dynamic hysteresis currents are used to illustrate specific cases of the cycling behavior for the Si-doped HfO2 thin film capacitors.

Characterisation and properties of Cu2ZnSnS4 thin films synthesised by sputtering from an alloy target

Cu2ZnSnS4 (CZTS) thin films were synthesised on glass substrates by sulphurising sputtered metallic precursors in H2S + N2 atmosphere at 500 °C. The influences of the radio frequency (RF) sputtering power on the structure, surface morphology, optical and electrical properties of the thin films were investigated. Scanning electron microscopy, X-ray diffraction, Raman and UV–vis NIR spectroscopy were used to characterise the films. All the CZTS thin films exhibited a dominant kesterite structure. With increasing sputtering power, secondary phases in the films reduced, and the surface became more compact. The optimum quality films with poor-Cu and rich-Zn were obtained when the sputtering power was 90 W, and the optical band gap, carrier concentration, resistivity and mobility were 1.47 eV, 2.07 × 1018 cm−3, 2.37 Ω cm and 1.38 cm2 s−1 v−1, respectively. The optical and electrical properties of the CZTS thin films in relation to the secondary phases were discussed.

Study of pulsed-DC sputtering induced Ge2Sb2Te5 thin films using facile thermoelectric measurement

Thermoelectric measurement is an exhaustive exercise for the case of thin films, requiring meticulous attention to the thermal contact interfaces and the instrumentation. Usually, different set-ups are combined for the temperature dependent measurement of different thermoelectric key quantities. Here, a facile 6-probe measurement set-up is presented, which can measure Seebeck coefficients and electrical properties of thin films in the temperature range of 300K–600K. Using this set-up, the thermoelectric properties of Ge2Sb2Te5 thin films, prepared with pulsed DC magnetron sputtering method are studied. The effects of working pressure, post-deposition thermal treatment and variation of film thickness on the microstructure, surface, electrical and thermoelectric properties are investigated systematically. Plasma diagnostics, performed using optical emission spectroscopy provided the information about various radicals' excitations and the electron temperature. Microstructural studies show the phase transformation from amorphous to metastable cubic phase. FESEM study exhibits highly dense films with uniform grains compactness. It has been found that lowering average crystallite size by optimum electron temperature and pressure conditions governs the enhancement in Seebeck coefficient. The throughput of process >400nm/min, and obtained Seebeck coefficients values 271.50μV/K are highly promising for industrial utilization.

Non-contact resistance measurement of transparent electrodes deposited on flexible display substrates under repetitive bending test by terahertz time domain spectroscopy

The objective of this study is to put forward a new non-contact resistance measurement method for repeating bending tests of transparent electrodes deposited on flexible display substrates. The study utilizes a terahertz time domain spectroscopy (THz-TDS) method to measure electrical properties of flexible polyethylene terephthalate/indium tin oxide samples up to 20,000 bending times. In addition, this study utilizes THz-TDS method to measure electrical characteristics of flexible substrates with hard-coat films. Accordingly, the percentage errors of measured sheet resistances based on THz-TDS method are less than or equal to 5.5% for comparison with a contact type four-point probe method or our previously reported flexible characteristic inspection system method. The values show a reasonable agreement with contact-mode sheet resistance measurements. Therefore, the electrical properties of thin films are measured offline or online easily by using this method.

Effect of Sb doping on the structural, electrical, and optical properties of SnO2 thin films prepared through spray pyrolysis

In this research, antimony-doped tin dioxide (ATO) films were deposited on glass substrates at T = 550 °C through spray pyrolysis. The effects of antimony doping on the structural, optical, and electrical properties of the thin films were investigated. Tin chloride (SnCl4·5H2O) and antimony chloride (SbCl3) were used as a host and a dopant precursor, respectively. X-ray diffraction (XRD) analysis indicated that the undoped SnO2 thin film exhibited a preferred (211) orientation. As the Sb doping concentration increased, a different preferred (200) orientation was observed. Field emission scanning electron microscopy analysis revealed polyhedron-like grains of the thin films. Atomic force microscopy analysis demonstrated that the minimum and maximum amounts of roughness were within the \(\frac{{\left[ {Sb} \right]}}{{\left[ {Sn} \right]}}\%\) molar ratio of 10 and 7.5 at.% concentrations, respectively. As the doping concentration increased, the average grain size initially increased and then decreased; electrical resistance initially decreased and subsequently increased; the carrier concentration and Hall mobility initially increased and then decreased; and Seebeck coefficient decreased. The optical band gap of the thin films ranged from 3.16 to 3.8 eV. Hall effect and thermoelectric studies revealed that the films exhibited an n-type conductivity.

Impact of the molecular structure of an indandione fragment containing azobenzene derivatives on the morphology and electrical properties of thin films

The solution casting method is low-cost processing method. Moreover, it is possible to prepare amorphous thin films by using this method, and thus, both optical quality and electrical properties could be improved in compare to polycrystalline films made by thermal evaporation in vacuum. Therefore, low-molecular-weight compounds that form amorphous structure from solution could be promising in organic electronics. In this work film morphology, molecule energy levels, and charge carrier mobility in thin films of indandione fragment containing azobenzene derivatives were studied. Deep charge carrier trapping states that drastically influenced charge carrier mobility were observed for polycrystalline films with the model compound 2-(4-((4-(dimethylamino)phenyl)diazenyl)benzylidene)-1H-indene-1,3(2H)-dione. This issue was overcome by attaching bulky groups to the model compound. An amorphous thin film without deep trapping states was obtained. Electron and hole mobilities of these materials at electric field 160 to 600 kV/cm were between 10−5 and 10−6 cm2V−1s−1 and between 10−6 to 10−7 cm2V−1s−1, respectively. Charge carrier mobility, molecular ionization energy, and electron affinity energy were influenced by bulky groups.

Effect of Annealing Temperature on NiO/ZnO Heterojunction Thin Films Prepared by Sol-Gel Method

In this research, NiO/ZnO heterojunction thin films were fabricated on a ITO substrate by a sol–gel technique. The as-prepared thin films were annealed at various temperatures. The effect of annealing temperature on structural, surface morphology and electrical properties of thin films was investigated by XRD, FESEM and I-V characteristic measurement. The XRD results revealed that NiO/ZnO thin film was polycrystalline and exhibited better crystallization when annealing temperature was increased. The current-voltage curve of all sample exhibited the diode behaviour.