Ti-doped Films Research Articles

Enhancing perovskite solar cells: Tailoring the properties of Ti-doped MAPbBr3 for reduced recombination and improved efficiency

By using the sol-gel method, (0 %, 4 % and 6 %) Ti-doped MAPbBr3 films were deposited on FTO-glass substrates. XRD confirmed cubic structure of all films and the 4 % Ti-doped film has a large grain size of 80 nm. UV–Vis spectroscopy analysis confirmed that the 4 % Ti-doped film has low band gap energy of 2.36 eV, and a high refractive index of 2.62. The tuning of the conduction and valence band edges speeds up the movement of charges between the layers. The solar cells of these films have been fabricated with the geometry of glass/TiO2/Ti-MAPbBr3/spiro-OMeTAD/Au. The 4 % Ti-MAPbBr3 based cell showed high current density (9.15 mA/cm2), open circuit voltage (1.03 V), fill factor (0.7407), and efficiency (6.9804 %). EIS showed that the 4 % Ti-MAPbBr3 cell has an increased electron transfer rate and lowers the possibility of recombination at the TiO2/perovskite interface.

Ti-doping of hematite films with multilayered particle size distribution by magnetron sputtering

α-Fe2O3 films with a layered distribution of nano and submicron particles were synthesized and Ti-doped successfully. Morphology, element and phase composition, electrochemical properties of one-layered, multilayered, and Ti-doped films were investigated. Doped multilayered hematite films have higher catalytic water oxidation efficiency than both undoped films.

Transported properties and low-temperature magnetic behaviors of Ti x Cr1− x O2 films

Electronic transport and magnetic properties of Ti x Cr1−x O2 epitaxial films with low Ti concentrations have been studied. Compared with pure CrO2 film, Ti-doped films exhibit a significant increase of resistivity and the magnetoresistance at low temperature is more difficult to saturate even under an external field of 5 Tesla. The DC magnetization and AC susceptibility measurements suggest that a cluster glass freezing behavior occurs at low temperature in Ti-doped films. After analyzing the AC susceptibility using dynamic scaling theory, we have obtained the cluster-glass transition temperature T G = 97.8 K, the dynamic exponent zv = 12.37, and the characteristic timescale τ 0 = 10−16, which lies in the range of conventional cluster glass systems.

Effect of metal nanoparticle doping concentration on surface morphology and field emission properties of nano-diamond films* *Project supported by the Science and Technology Major Project of Shanxi Province, China (Grant No. 20181102013) and the Fund from the “1331 Project” Engineering Research Center of Shanxi Province, China (Grant No. PT201801).

Nano-diamond particles are co-deposited on Ti substrates with metal (Ti/Ni) nanoparticles (NPs) by the electrophoretic deposition (EPD) method combined with a furnace annealing at 800 °C under N2 atmosphere. Modifications of structural and electron field emission (EFE) properties of the metal-doped films are investigated with different metal NPs concentrations. Our results show that the surface characteristics and EFE performances of the samples are first enhanced and then reduced with metal NPs concentration increasing. Both the Ti-doped and Ni-doped nano-diamond composite films exhibit optimal EFE and microstructural performances when the doping quantity is 5 mg. Remarkably enhanced EFE properties with a low turn-on field of 1.38 V/μm and a high current density of 1.32 mA/cm2 at an applied field of 2.94 V/μm are achieved for Ni-doped nano-diamond films, and are superior to those for Ti-doped ones. The enhancement of the EFE properties for the Ti-doped films results from the formation of the TiC-network after annealing. However, the doping of electron-rich Ni NPs and formation of high conductive graphitic phase are considered to be the factor, which results in marvelous EFE properties for these Ni-doped nano-diamond films.

Influence of Ti doping on the microstructural and electrochromic properties of dip-coated nanocrystalline V2O5 thin films

The nanocrystalline V2O5 thin films were prepared via a dip-coating method by controlled hydrolytic polycondensation of the vanadium (V) oxytriisopropoxide (VO(OC3H7)3) in isopropanol. For Ti doping, titanium (IV) isopropoxide (Ti(OC3H7)4) was used. The as-deposited films after thermal treatment at 500 °C under ambient air for 30 min were subjected to characterizations for their structural, morphological, and electrochromic properties. The X-ray diffraction (XRD) analyses of the films confirm an orthorhombic phase of vanadium pentaoxide (PDF # 41-1426), which is also supported by Fourier transform infrared (FTIR) analyses. The analyses of electrochromic properties of the films divulge that the 5 at% Ti-doped film has the fast switching time (coloration time: 0.59 s and bleaching time: 0.42 s), high net charge density and good electrochromic reversibility. The Nyquist impedance plots have been evaluated by fit and simulation analysis using Nova software, taking into account an equivalent electrical circuit model.

Magnetic properties and thermal stability of Ti-doped CrO2 films

Chromium dioxide (CrO2) is a striking half metal material which may have important applications in the field of spintronics. However, pure CrO2 film is metastable at room temperature and the synthesis process can be only performed in a narrow temperature range of 390–410 °C with TiO2 used as substrate material. Here, we report the preparation and investigation of (1 0 0) oriented Ti-doped CrO2 films on TiO2 substrates. It is found that Ti-doped films can maintain pure rutile phase even after a 510 °C post-annealing, showing much better thermal stability than pure CrO2 films. Ti-doped films can be prepared in a wider temperature window (390–470 °C), which may be attributed to the improvement of thermal stability. The broadening of process window may be beneficial for further improvement of film quality by optimizing growth temperature in a larger range. In addition to the improvement of thermal stability, the magnetic properties of Ti-doped CrO2 are also found to be tuned by Ti doping: saturation magnetizations of Ti-doped films at room temperature are significantly lower, and magnetic anisotropy decreases as the Ti-concentration increases, which is beneficial for decreasing switching current density in STT-based spintronic devices.

Charge Transport at Ti-Doped Hematite (001)/Aqueous Interfaces

Solid-state transport and electrochemical properties of Ti-doped hematite (α-(TixFe1-x)2O3 (001) epitaxial thin films (x = 0.15, 0.21, and 0.42) were probed to achieve a better understanding of doped hematite for photoelectrochemical (PEC) applications. Room temperature resistivity measurements predict a resistivity minimum near x = 0.25 Ti doping, which can be rationalized as maximizing charge compensating Fe2+ concentration and Fe3+ electron accepting percolation pathways simultaneously. Temperature dependent resistivity data are consistent with small polaron hopping, revealing an activation energy that is Ti concentration dependent and commensurate with previously reported values (≈ 0.11 eV). In contact with inert electrolyte, linear Mott–Schottky data at various pH values indicate that there is predominantly a single donor for Ti-doped hematite at x = 0.15 and x = 0.42 Ti concentrations. Two slope Mott–Schottky data at pH extremes indicate the presence of a second donor or surface state in the x = 0.21 Ti-doped film, with an energy level ≈0.7 eV below the Fermi level. Mott–Schottky plots indicate pH and Ti concentration dependent flatband potentials of −0.2 to −0.9 V vs SHE, commensurate with previously reported data. Flatband potentials exhibited super-Nernstian pH dependence ranging from −69.1 to −101.0 mV/pH. Carrier concentration data indicate that the Fermi energy of the Ti-doped system is Ti concentration dependent, with a minimum of 0.15 eV near x = 0.25. These energy level data allow us to construct an energy band diagram for Ti-doped hematite electrode/electrolyte interfaces, and to determine a Ti-doping concentration that reduces bulk resistivity while also reducing the formation of surface states for these photoanodes.

Structural, electrical and magnetoresistance of titanium-doped iron (II,III) oxide (Fe3O4) thin films deposited on strontium titanate, alumina, silicon, and Float Glass

Titanium (Ti) doping effects on the structural and transport properties of half-metallic Fe3O4 iron (II,III) oxide (magnetite – Fe3O4) films grown on various substrates such as strontium titanate (SrTiO3 (100)), silicon (Si (111)), alumina (Al2O3 (0001)), and Float Glass (FG) by pulsed-laser deposition (PLD) are studied. X-ray diffraction (XRD) pattern infers that parent and Ti doped magnetites have cubic spinel structure. The first order phase transformations at the Verwey transition Tv for Fe3O4 thin films are 123K (SrTiO3), 120K (Si), 123K (Al2O3), and 121K (Float Glass). Raman spectra infer five Raman-active modes (A1g, Eg, and three T2g modes) and gradual changes are evident on Ti doped films on different substrates. Magnetoresistance (MR) curves show linear magnetic field dependence for the parent films, while an increase in MR and departure from linear field dependence is observed for Ti-doped films. MR curves display highest change for doped and undoped films grown on Al2O3 (0001) substrate. For parent Fe3O4 films MR is of −0.48% at room temperature which increases below the Verwey transition up to −1.12% at 100K, while in Ti doped films MR is of −1.56% at room temperature which increases up to −3%.

Physical and photoelectrochemical characterization of Ti-doped hematite photoanodes prepared by solution growth

We present the fabrication and characterization of Ti-doped hematite (α-Fe2O3) films for application as photoanodes in photoelectrochemical (PEC) cells for water splitting. It is demonstrated that Ti doping significantly improves the PEC activity as the photocurrent at 1.0 V vs. Ag/AgCl electrode for a 400 nm thick Ti-doped film (0.66 mA cm−2) was found to be ∼14 times higher than that of an undoped film (0.045 mA cm−2). The films were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and ultrafast transient absorption spectroscopy to obtain information about their structural, electronic, and charge carrier dynamic properties. Based on characterization of the chemical states of the involved elements as well as the charge carrier dynamics of the films with Ti doping, it appears that the photocurrent enhancement is related to an increase in charge carrier density or reduced electron–hole recombination. The highest incident photon conversion efficiency (IPCE) measured for this system was 27.0% at 360 nm at a potential of 1.23 V vs. reversible hydrogen electrode (RHE), which was obtained on a 400 nm thick Ti-doped α-Fe2O3 film.

Photoluminescence of Titanium-Doped Zinc Orthosilicate Phosphor Gel Films

Titanium-doped zinc orthosilicate (α-Zn2SiO4:Ti) phosphor thin films were deposited on silicon wafer substrates by the sol–gel process. The crystallization processes and photoluminescence properties of the films were investigated. X-ray diffraction revealed that the dried films were amorphous and converted into single-phase willemite structure following annealed at 600 °C and above. Upon thermal annealing at 800 ° –1000 °C, Ti-doped willemite thin films had the average crystallite sizes of 17∼28 nm. The luminescence properties of phosphor films were characterized by excitation and emission spectra. Photoluminescence spectra of Ti-doped films exhibited prominent blue emission bands centered at 402 nm under an excitation wavelength of 225 nm. The emission intensity was dependent on the level of titanium doping, annealing temperature, and film thickness.

Photoelectrochemical Performance of Nanostructured Ti- and Sn-Doped α-Fe2O3 Photoanodes

Thin films of α-Fe2O3 doped with either Ti or Sn were prepared by coevaporating iron and titanium/tin in a reactive oxygen ambient, and their physical, chemical, and photoelectrochemical properties were studied. It was found that manipulating the deposition angle had a profound effect on the photoelectrochemical water oxidation performance of 4% Ti-doped α-Fe2O3 films, and a maximum in photocurrent at 1.4 V vs RHE (Reversible Hydrogen Electrode) was achieved for films grown at 75° incidence. It was also found that the nanocolumnar morphology and superior porosity attained using glancing angles improved the relative conversion of visible-light (λ > 420 nm) photons compared to dense films deposited at normal incidence. Sn-doped films were also prepared for comparison using the same deposition conditions, and although they were substantially better than undoped films, their performance was somewhat below that of Ti-doped films. The Ti-doped films deposited using optimum conditions resulted in incident photon...

Improved photoelectrochemical responses of Si and Ti codoped α-Fe2O3 photoanode films

We studied photoelectrochemical performance of the undoped, Si-doped, Ti-doped, and codoped α-Fe2O3 film prepared by ultrasonic spray pyrolysis. Since the ions radius of Si4+<Fe3+<Ti4+, Si and Ti codoping can balance the ion radius difference between Fe3+ and Si4+ (or Ti4+) and increase the donor concentration. Their donor concentrations, calculated from slopes of the Mott–Schottky plots, are 9.10×1018 cm−3, 1.89×1020 cm−3, 2.04×1020 cm−3, and 7.06×1020 cm−3, respectively. Incident photon to current efficiency of the codoped film is 34% at 365 nm and 0.6 V versus Ag/AgCl, much higher than 10%, 20%, and 22% for the undoped, Si-doped, and Ti-doped film, respectively.

Characteristics of W- and Ti-Doped VO[sub 2] Thin Films Prepared by Sol-Gel Method

W- and Ti-doped thin films were deposited onto sapphire by the sol-gel method. Both films were grown with (020)-preferred direction. Doping of W had a great effect on the transition behaviors. A 1.2 atom % W-doped film showed a largely reduced resistance in the insulator state and decreased the transition temperature to . However, Ti-doped film had a little change of the transition temperature, and it was , even for the 20 atom % Ti doping. The resistance in the metal state was very large, which means a markedly small change of the resistance at the transition temperature. Further study is required for understanding the effects of doping film with metal ions.

Electrical properties and leakage current behavior of un-doped and Ti-doped lead zirconate thin films synthesized by sol–gel method

Un-doped and Ti-doped (5, 10 and 15 mol%) antiferroelectric and ferroelectric lead zirconate–PbZrO 3 (PZ) thin films were prepared by sol–gel spin coating method. All PZ films crystallized in the perovskite phase with full [111] pseudocubic orientation with a uniform microstructure. The paraelectric–ferroelectric phase transition temperature was found to shift to lower values and the electrical properties were found to degrade as a result of decreasing film thickness. The leakage current of the un-doped PZ films were dominated by the space-charge-limited current, whereas Poole–Frenkel conduction mechanism was found to be dominant at the Ti-doped films at high electric fields.

Electrochromic Properties of Sputtered Ti-Doped WO3 Films

Ti-doped WO3 films were prepared by the mid-frequency dual-targetmagnetron sputtering method. The structure and electrochromicproperties of the Ti-doped WO3 films were analysed by X-Raydiffraction (XRD), Raman spectroscopy, spectrophotometer, cyclicchronoamperometry and atomic force microscopy (AFM). The resultsindicate that the crystallinity decrease after the doping oftitanium, the channels for ion injection and extraction increase,the responding speed with 5.1% titanium doped becomes faster, andits circle life increases more than four times compared with theundoped WO3 film. In the coloured state, the W-O-W bondsdecrease, but the W = O bonds increase. Since the W-O-W bonds breakdown for Li+ ions' injection and more W = O bonds form, it ismore convenient to inject Li+ ions into the Ti-doped film thanundoped film because more W-O-W bonds break down in the colouredstate.

Ti-doped copper nitride films deposited by cylindrical magnetron sputtering

Pure and Ti-doped copper nitride films were prepared by cylindrical magnetron sputtering on glass substrates at room temperature. The preferred orientation for copper nitride films changes from [1 1 1] for undoped film to [1 0 0] for Ti-doped films. The variation of surface morphology correlates to that of preferred orientation resulting from the variation of Ti-doped content. The electrical resistivity and optical band gap increases as the Ti-doped content increases.

Formation and pinning properties of growth-controlled nanoscale precipitates inYBa2Cu3O7−δ/transition metal quasi-multilayers

To study the possibility of enhancing the pinning forces inYBa2Cu3O7−δ films through the introduction of nanosized precipitates, quasi-multilayers ofYBa2Cu3O7−δ and a transition metal(TM = Ti,Zr,Hf) were depositedon single-crystal SrTiO3 substrates using pulsed laser deposition. The transition metal layer thickness was chosen to be less thanone unit cell, resulting in separated nanoscale islands that form inclusions with perovskite structureBaTM O3 during film growth. These inclusions grow biaxially textured within the film.Whereas the Ti-doped films show a very strong decrease in the critical temperatureTc and, hence, a strong decrease in the critical current densityJc with increasing TM amount for all temperatures, Hf and Zr doping show an increase inJc for the smallest amounts of doping. An irreversibility field as high as 10.3 T at 77 K wasobserved in the case of low Hf content.

The study of doped DLC films by Ti ion implantation

Diamond-like carbon (DLC) films were prepared by unbalanced magnetron sputtering. Ti-doped DLC films were obtained by Ti ion implanted into the achieved DLC films using metal vapor vacuum arc (MEVVA). The effects of Ti+ ion implantation on the surface morphology, structure, and tribological properties of the DLC films were investigated by means of atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and friction measurement. The smooth and uniform Ti-doped film with the surface roughness of 0.595 nm was obtained. Raman result revealed that the formation of DLC films and sp2 bonds content increase by Ti+ ion implantation. TEM showed that the nanocrystalline phases of TiC were formed in the films. Ti+ was implanted into the interface between C and substrate, detecting the sputtering depth profiles of the film by XPS; thus, the interface was widened due to reserve diffusion. Tribological test experiment indicated that friction coefficient of the films decreased to approximately 0.15 by Ti+ ion implantation.

Electrochromic properties of NiO-based thin films prepared by sol–gel and dip coating

A new method for chemical deposition of NiO x H y -based films was developed. The films obtained have electrochromic properties and good adhesion to the substrate. The precursor sol consists of an alcoholic solution of NiCl 2 and Ti alcoxide. Films deposited on indium–tin-oxide substrates were prepared by dip coating. The electrochromic efficiency of thin films prepared under different conditions was determined. We report on the effects of (a) Ni concentration, (b) Ti content and (c) temperature of firing on the electrochromic efficiency. Electrochromic efficiencies measured at λ=632.8 nm of films with different thicknesses (∼100–200 nm) range from 10 to 42 cm 2 C −1, with a variation in transmittance up to 30%. The colouring response time is strongly dependent on Ti content. For Ti-doped films this time is 5–80 times longer than for undoped ones. The variations in monochromatic transmittance during voltammetric cycles suggest that all the electric charge consumed by redox reactions is involved in the colouring process.

Microstructure And Wear Resistance Of Doped Diamondlike Carbon Prepared By Pulsed Laser Deposition

ABSTRACTWe have investigated the microstructure and tribological properties (wear resistance) of diamondlike carbon (DLC), DLC doped with Cu and DLC doped with Ti deposited by a sequential pulsed laser ablation of two targets onto Si(100) substrates. The composition of these films was determined by Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy(XPS). Raman spectroscopy and detailed analysis of the electron diffraction pattern of the films showed typical features of DLC with a structure dominated by sp3 bonded carbon. Wear resistance measurements made on these samples by means of the “crater grinding method” showed that DLC + 2.75%Ti has the highest wear resistance, while that of undoped DLC has the lowest among the samples. The improvement of wear behavior of the doped films was attributed to the reduction of internal compressive stress due to the presence of more compliant atoms, as indicated by the G-peak position shift to smaller Raman shift. The XPS studies showed the evidence for the formation of Ti- C bonding in the Ti doped films. Thus we expect metal-doped DLC coatings can have better tribological properties than the undoped, highly stressed DLC coatings.