Effect Of Iodine Doping Research Articles

Properties of I-Doped CuI Thin Films by Chemical Vapor Deposition (CVD)

In this paper, we present the properties of I-doped CuI thin films at different concentration of iodine dopant (e.g. 10mg, 20mg, 30mg, 40mg and 100mg). The doping of CuI was done by using double furnace chemical vapor deposition (CVD) method. The effects of I-doped CuI to its surface morphology and electrical were studied. The effect of iodine doping to surface morphology was measured by field emission scanning electron microscopy (FESEM). The morphology of all thin films shows insignificance changes in grain size, grain boundaries and particle structure as the doping concentration varies. For the electrical properties, high current at constant voltage of-5V to 5V was obtained. The resistivity of 10-1 was obtained for undoped CuI thin films. While, for the series of I-doped CuI thin films, the resistivity of 10-2 was obtained. The excess of hole conductor in the I-doped CuI thin films enhances the electrical conductivity of the films.

Effect of iodine doping on the electrical transport mechanism in plasma polymerized 2,6-diethylaniline thin films

The current density–voltage characteristics of pure and iodine doped plasma polymerized 2,6-diethylaniline (PPDEA) thin films of different thicknesses ranging from 150 to 450nm with aluminum (Al)/PPDEA/Al structure have been investigated at room temperature. The direct current electrical conductivity has showed a higher value due to iodine doping of PPDEA thin film. In contrast to pure PPDEA thin films where the most probable conduction mechanism is electrode limited Schottky type, Poole–Frenkel (PF) conduction mechanism is found to be operative in iodine doped PPDEA thin films. The PF conduction mechanism in iodine doped PPDEA thin films may have generated due to the charge transfer complex formation through donor type monomer and acceptor type iodine. The presence of charge transfer complex is confirmed by a new absorption shoulder/peak in ultraviolet–visible spectrum of iodine doped PPDEA thin film.

Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells

We report two novel types of hierarchically structured iodine-doped ZnO (I-ZnO)-based dye-sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 I-ZnO and N719 I-ZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of I-ZnO, favoring enhanced exciton life. Mott-Schottky analysis results indicated a negative shift of the flat-band potential (V(fb)) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage (V(oc)). To reveal the effect of iodine doping on the effective separation of e(-)-h(+) pairs which is responsible for cell efficiency, direct visualization of light-induced changes in the surface potential between I-ZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine-doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident-photon-current efficiency, and cyclic voltammetry investigations on I-ZnO cells were carried out. The results revealed several favorable features of I-ZnO cells, that is, longer electron lifetime, lower charge-transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.

Iodine Doping of Amorphous Carbon Thin Films Deposited by Thermal CVD

A simple thermal chemical vapor deposition method is employed for the deposition of amorphous carbon thin films by natural precursor camphor oil onto the glass substrates and the iodine doping process. In this work, we have studied the effect of iodine doping on the evolution of electrical properties and the optical and structural properties of amorphous carbon thin films. The amorphous carbon thin films were characterized by using Raman spectroscopy, UV-VIS-NIR spectroscopy, current-voltage (I-V) measurement, Fourier transform infrared (FTIR) and FESEM. The I-V study reveals that the electrical conductivity was increased with the iodine doping. The iodine doped thin films induced graphitization by decreasing the optical band gap. Raman and FTIR result indicates that amorphous carbon thin films consist of a mixture of sp2 and sp3 bonded carbon atoms. The FESEM shows the amorphous nature of the thin films.

Effect of iodine doping on the photoconduction behaviour of pristine and high-energy heavy ion-irradiated kapton-H polyimide

The effect of iodine doping on the photoconduction behaviour of pristine and 75 MeV oxygen ion-irradiated (fluence: 3.12×1012 ions/cm2) kapton-H polyimide film in the visible region has been investigated for different doping hours at various operating temperatures ranging 40–250°C and at different electric fields (40–400 kV/cm). The formation of charge transfer complexes in polymers effectively decreases the trapping sites by handling the charge carriers. A decrease in the photocurrent in ion-irradiated samples at higher exposure time for iodine vapours as compared with pristine samples has been associated with the enhancement in the trapping sites which may deplete the charge carriers and a loss in the photoactive groups owing to radiation-induced demerisation. The evidence of Frankel-type conduction (based on the estimation of Schottky coefficients) mechanism in irradiated samples is observed. A strong dependence of photocurrent on temperature in doped pristine and ion-irradiated samples reconfirms the thermal ionisation process of exciton for photogeneration of charge carriers.

Effect of iodine doping of phthalocyanine on the photocurrent generation in a phthalocyanine/C60 heterojunction

Photocurrent generation in an indium–tin oxide (ITO)/iodine-doped Ni-phthalocyanine (NiPc-Ix)/C60/In/Al heterojunction device with x~1 was studied. By keeping the device in air after preparation, the device slowly reached a stationary state in which the sign of the photocurrent is opposite to that of a non-doped ITO/NiPc/C60/In/Al device although the rectification direction for the dark current is the same. By a simulation of incident photon-to-current conversion efficiency spectra and a measurement of internal electric field by electroabsorption spectroscopy, it was elucidated that, in the doped device, the band bending near the phthalocyanine/C60 interface is absent and the photocurrent is generated by a weak Schottky barrier at the C60/In interface. It is also shown that the C60 film encapsulates the doped iodine into the NiPc-Ix layer to stabilize the doping level and prevent the reaction of iodine with In.

Poly(ester)s and poly(amide)s with fluorene and diphenyl‐silane units in the main chain: Effects of iodine doping on the structure and electrical conductivity

AbstractIntramolecular charge transfer interaction between the electron donor and electro acceptor units within the polymeric structure and its optoelectronic properties were studied. The monomer, 9H‐fluorene‐2,7‐dicarboxylic acid, was prepared from 9H‐fluorene‐2,7‐dicarbonitrile using CuCN/N,N‐dimethylformamide followed by the decomposition of the complex with FeCl3x6H2O in HCl and KOH/H2O. The formation of two new classes of polymers was reported at different reaction times. The poly(ester) (PEF) was synthesized by the reaction of the diacid monomer with bis(4‐hydroxiphenyl)diphenylsilane using tosyl chloride/pyridine/dimethylformamide system as condensing agent. Alternatively, the poly(amide) (PAF) was synthesized by the direct polycondensation of the diacid monomer and bis(4‐aminophenyl)diphenylsilane in N‐methyl‐2‐pyrrolidine solution containing dissolved calcium chloride. The resulting new polymers were obtained in good yields and were characterized by FTIR, NMR (1H, 13C, and 29Si), ESI, Raman, UV (optical gap) and fluorescence spectroscopy. The thermal properties were characterized by DSC and TGA. The electrical conductivity of the polymers was measured before and after exposure to iodine vapor, utilizing films of different thickness. Ellipsometric studies were used for the determination of the film thickness. Morphological differentiation was carried out by SEM‐EDX analysis. Oxidation of the polymer films of low thickness decreased their conductivities, mainly due to the small structural changes. For a polymeric sample with a higher thickness, the doping process slightly increased the conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Physical characterization of functionalized spider silk: electronic and sensing properties

This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of β-sheet (crystalline) and amorphous (helical) structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 °C, has a strong effect on the morphology of silk bundles (increasing their size), on the process of pyrolization (suppressing mass loss rates) and on the resulting carbonized fiber structure (that becomes more robust against bending and strain). The effects of iodine doping and other functional parameters (vacuum and thin film coating) motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR) to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and β-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR) spectroscopy, revealing a partial transformation of β-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof-of-concept applications of functionalized spider silk are presented for thermoelectric (Seebeck) effects and incandescence in iodine-doped pyrolized silk fibers, and metallic conductivity and flexibility of micron-sized gold-sputtered silk fibers. In the latter case, we demonstrate the application of gold-sputtered neat spider silk to make four-terminal, flexible, ohmic contacts to organic superconductor samples.

Effect of Iodine Doping on Surface and Optical Properties of Polyterpenol Thin Films

This study presents the effect of iodine doping on optical and surface properties of polyterpenol thin films deposited from non-synthetic precursor by means of plasma polymerisation. Spectroscopic ellipsometry studies showed iodine doping reduced the optical band gap from 2.82 eV to 1.50 eV for pristine and doped samples respectively. Higher levels of doping notably reduced the transparency of films, an issue if material is considered for applications that require high transparency. Contact angle studies demonstrated higher hydrophilicity for films deposited at increased doping levels, results confirmed by XPS Spectroscopy and FTIR. Doping had no significant effect on the surface profile or roughness of the film.

The effects of iodine doping on the thermoelectric properties of [formula omitted] at low temperatures

The thermoelectric properties of iodine-doped compounds Zn 4(Sb 1− x I x ) 3 ( x = 0 , 0.005, 0.01, 0.015) have been studied at temperatures from 5 to 310 K. The results indicate that the low-temperature ( T < 300 K ) thermal conductivity λ of moderately doped Zn 4(Sb 0.995I 0.005) 3 reduced remarkably as compared with that of Zn 4Sb 3 due to the enhanced impurity (dopant) scattering of phonons. The electrical resistivity and Seebeck coefficient were found to increase monotonically with the increase in the iodine content, which would reflect the decrease in carrier concentration due to the substitution of I for Sb. Moreover, the lightly doped compound Zn 4(Sb 0.995I 0.005) 3 exhibited the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, was about 1.2 times larger than that of β - Zn 4Sb 3 obtained in the present study at 300 K.

Electrical Properties of Iodine-Doped CdTe Epitaxial Films on Si Substrates Grown by MOVPE

We studied the effect of iodine doping of CdTe films on Si substrates grown by MOVPE at different growth conditions. A high resistivity film was obtained by adjusting the growth temperature, Te/Cd precursor flow ratio and the dopant flow-rate. Our results show the film resistivity does not change linearly with the dopant flow-rate. The resistivity remains low and similar to that of undoped value for low dopant flow-rate, but increases abruptly when the dopant flow-rate is increased beyond certain value. Photoluminescence measurements of the films confirmed the dopant incorporation in the crystal. We explained the result of resistivity change due to the compensation of excess shallow acceptors by deep intrinsic donors.

Photovoltaic properties of liquid-state photoelectrochemical cells based on PPAT and a composite film of PPAT and nanocrystalline titanium dioxide

We have studied the optical and photoelectrical properties of liquid state photoelectrochemical cells (PECs) based on photoactive electrodes based on poly (phenyl azo methane thiophene) (PPAT) and a composite film of nano-crystalline titanium dioxide (nc-TiO 2) and PPAT. The device fabricated with nc-TiO 2/PPAT photoactive electrode shows better performance with an open circuit voltage ( V oc) 0.56 V, short circuit photocurrent ( J sc) = 0.87 mA/cm 2 and fill factor (FF) = 0.58 under illumination with white light intensity of 10 mW/cm 2. We have analyzed the experimental results by comparing the IPCE spectra of both devices. It is observed that the device with nc-TiO 2/PPAT photoactive electrode shows better photovoltaic response as compared to the device based on PPAT photoactive electrode. This indicates that PPAT shows its p-type semiconducting behavior in the device based on PPAT, while in the device based on nc-TiO 2/PPAT photoactive electrode, the PPAT acts as a sensitizer to nano-crystalline TiO 2. The PEC based on TiO 2/PPAT photoelectrode exhibit an exponential increase of low frequency device capacitance due to the diffusion of electrons along TiO 2 network. Effect of iodine doping in PPAT on the photovoltaic performance of PEC have been also studied.

Syntheses, structures, electric conduction, electrochemical properties and antimicrobial activity of azomethine monomer and oligomer based on 4-hydroxybenzaldehyde and 2-aminopyridine

The effects of temperature (50-80°C), reaction time (up to 15h) as well as type and concentration of oxidizing agent (NaOCl, air O2, H2O2) on the course of oxidative polymerization of 4-[(pyridin-2-yl-imino)methyl]phenol (4-PIMP) in aqueous alkaline medium, and on the yield of the oligomers formed (O-4-PIMP) were investigated. The optimal conditions of the process have been found. Reaction products were characterized using the following methods: 1H NMR, 13C NMR, FT-IR, UV-VIS, gel permeation chromatography and thermal analyses TG-DTA. Mn values of O-4-PIMP are in the range 1250-4450. The oligomer shows better thermal stability than the monomer. On the basis of voltammetric measurements' results the electrochemical properties of 4-PIMP and O-4-PIMP were characterized in detail, including an effect of iodine doping of O-4-PIMP on the electric conduction. The comparison of antibacterial activity of 4-PIMP and O-4-PIMP against 8 bacterial strains has been done.

Assembling Nanowires from Mo−S Clusters and Effects of Iodine Doping on Electronic Structure

Using ab initio calculations, we find high stability of octahedral Mo6S8 clusters, which can further be condensed to form Mo3nS3n+2 (n, an integer) nanowires. These linear structures are energetically more favorable compared with other closed-packed polyhedral isomers of Mo-S clusters. The octahedral units in nanowires are stabilized by strong Mo-Mo interactions and p-d hybridization between Mo 4d and S 2p orbitals. There is a free electron-like band that crosses the Fermi energy in infinite nanowires and leads to their metallic character. Iodine doping acts as electron donor and can be used to tailor the electronic conductivity. For Mo12S8I4 nanowires, both electrons and holes are found to contribute to conduction. These nanowires are energetically more favorable than the experimentally obtained Mo12S6I12 nanowires.

Effect of iodine doping on the kinetics of microwave photoconductivity in cadmium telluride

Effect of iodine doping on the kinetics of microwave photoconductivity in cadmium telluride

Iodine doping in amorphous carbon thin-films for optoelectronic devices

We report the effects of iodine doping on the optical and structural properties of amorphous carbon thin-films grown on silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (CVD) at low temperature (<100 °C). For film deposition, we used Ar and CH 4 as plasma source gases. The films were characterized by UV/Vis/NIR spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements. The optical band gap of the films decreased from 3 to 0.8 eV corresponding to non-doping to iodine doping conditions. The XPS results confirm the successful doping of iodine in the films. The Raman results show that iodine doping induced more graphitization in the films.

Activated Carbons for High Power Energy Storage: Below the Surface of Non-Faradaic Reactions

ABSTRACTThe effect of iodine doping on the electrochemical performance of activated carbons for non-aqueous symmetric and asymmetric hybrid supercapacitors was investigated. The incorporation of iodine via high energy mechanical milling techniques significantly modified the physical and electrochemical properties of activated carbon precursors. The increasing amount of iodine into carbons leads to a unique combination of lower surface area coupled with higher volumetric and gravimetric electrochemical capacitance. Iodine modification of the carbon resulted in a 100% increase in volumetric capacitance. This improvement was a result of improved non-faradaic capacitance and the development of faradaic capacity.

Effect of iodine doping on the luminescent properties of the photochromic material CdBr2:Cu+

The effect of iodine doping on the roentgenoluminescence (RL) and thermoluminescence (TL) of CdBr2:Cu+ is studied using CdBr2:(Cu+ ,I-) crystals grown by the Bridgman-Stockbarger method from melts containing 0.5 wt % CuBr and 0.15, 0.5, or 5.0 wt % CdI2. The results demonstrate that, with increasing iodine content, the RL intensity first rises and then drops; in addition, the RL band shifts from 560 to 490–510 nm. At low CdI2 levels, the TL curve shows peaks at 110, 130, 152, and 168 K, characteristic of CdBr2:Cu+. At the maximum iodine concentration, the TL curve shows a weak peak at 115 K. The TL spectrum of lightly iodine-doped crystals is dominated by the 490-nm emission, which is attributable to heteronuclear anion excitons. The formation of nI- clusters in heavily doped CdBr2:(Cu+,I-) crystals reduces the concentration of (BrI)- hetero-nuclear centers. The nature of the trapping levels responsible for the TL of the crystals is discussed.

Effects of iodine doping on optoelectronic properties of diamond-like carbon thin films deposited by microwave surface wave plasma CVD

We report the effects of iodine (I) doping on the electrical and optical properties of diamond-like carbon (DLC) thin films grown on silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition at low temperature (<100 °C). For film deposition, we used argon gas with methane or camphor dissolved with ethyl alcohol composition as plasma source. The optical gap and photoconductivity measurements of the samples were carried out before and after the iodine doping. The results show that optical gap dropped from 3.4 to 0.9 eV corresponding to nondoping to iodine-doping conditions, respectively. The photovoltaic measurements show that the open-circuit voltage ( V oc) and short-circuit current density ( J sc) of I-doped DLC film deposited on n-type silicon substrate under light illumination (AM1.5, 100 mW/cm 2) were approximately 177 mV and 1.15 μA, respectively, and the fill factor was found to be 0.217.

Effect of iodine doping on the bandgap of plasma polymerized aniline thin films

Pure and iodine-doped polyaniline thin films are prepared by ac plasma polymerization technique. Doping of iodine is carried out in situ as well as by employing iodine chamber methods. The structural analyses of pure and iodine-doped polyaniline thin films are carried out by FTIR spectroscopic studies. Optical bandgaps of these films are evaluated from UV-VIS absorption studies. Direct and indirect transition energy gaps are determined from Tauc plots. The structural changes of polyaniline upon doping and the reduction of optical bandgap are explained on the basis of the results obtained from FTIR spectroscopic and UV-VIS absorption studies.