Copper Phthalocyanine Thin Films Research Articles

Electrochromism of copper phthalocyanine thin films

Copper phthalocyanine thin films were deposited using a vacuum evaporation technique at 2 different substrates temperatures of 30 °C and 15 °C. Their electrochromic behaviour in a lithium perchlorate solution was examined. The films deposited at the substrate temperature of 30 °C were polycrystalline, and did not exhibit colour changes under the bias potential of 2.0 V. However, the thin films deposited at the substrate temperature of 15 °C were amorphous and showed colour changes from dark blue to purple and to light blue under the bias potential of 1.0 V.

Influence of NO 2 on the electrical conductivity of lutetium phthalo-naphthalocyanine thin films

This paper describes the results of the action of gaseous NO 2 on the semiconducting properties of lutetium phthalo-naphthalocyanine thin films. They are compared to those already presented on the interaction between NO 2 and lutetium diphthalocyanine or copper phthalocyanine thin films. The difference in behaviour among the three compounds in the presence of NO 2 is due to (i) the different intrinsic charge carrier concentrations, (ii) the more or less good ability to undergo redox reactions with dopants, and (iii) the polycrystalline or quasi-amorphous structures of the thin films which influence the diffusion rate of the gas within the layers.

Gas sensitive properties of copperphthalocyanine thin films

Copperphthalocyanine (CuPc) thin films, about 250 nm thick, were prepared by vacuum evaporation on glass substrates, and their gas sensitive properties were examined. Two kinds of CuPc films, polycrystalline and amorphous, were obtained by changing the substrate temperature. A pair of Au electrodes were vacuum deposited on the CuPc films, and the conductivity change associated with introduction of NO 2 gas into the measuring chamber was measured. The conductivity increased by several orders of magnitude associated with introduction of NO 2 gas (1000 ppm) for both the specimens at room temperature. The gas sensitivity of the amorphous CuPc film was higher than that of the polycrystalline film. This result was attributed to the fact that stacking of CuPc molecules was more loose in the amorphous film than in the polycrystalline film. The gas sensitivity and the response were found to be improved with light irradiation.

Reversible Electrochromism of Copper Phthalocyanine Thin Film

Abstract The electrochromism of copper phthalocyanine thin films was examined in detail under various conditions. The application of a positive voltage to copper phthalocyanine thin film exhibited two oxidation peaks in the range from 0 to 1.4 V. Although the color of the film changed from sky blue to pale gray upon scanning the voltage in this region, irreversible electrochromism was observed, leading to a deterioration of the film. The two oxidation peaks were concluded to represent two types of appearances of one reaction with different overpotentials caused by the structure of the crystal grains of the film. Control of the scan range to admit only the first oxidation peak provided a reversible electrochromism between sky blue and bluish purple. Electrolyte anions are also of great importance to accomplish reversible electrochromism. Thus, the anions should be stable for the application of a positive voltage, and their Stokes radii should be neither too large nor too small in order to achieve reversible electrochromism. Rather small anions provide almost Nernstian cyclic voltammograms and the quick color change.

Electrical resistance of copper phthalocyanine thin films as influenced by substrates, electrodes and physical features of the films

The influence of several features upon the electrical resistance of gas-sensitive copper phthalocyanine (CuPc) thin films has been investigated. The main factors studied concern the substrate nature (Al 2O 3 or Si/SiO 2), electrode layout, film thickness and deposition rate. Subsequent annealing round 200°C may induce more or less deep structural changes subject to the type of substrate. Molecular deterioration may also occur by way of electrochemical processes under some conditions. The effect of humidity on the electricla resistance also appears to be substrate dependent.

The Review of Laser Engineering Topical Papers on Thin Films Fabrication and Control. Fabrication of Copper-Phthalocyanine Thin Films by Laser Ablation Deposition.

Copper-phthalocyanine (CuPc) thin films were successfully fabricated via pulsed laser ablation. In order to maintain a molecule architechture in the deposited films, laser fluence must be kept near the laser ablation threshold. Despite of poor crystallinity exhibited in the films, the CuPc film still maintains its electrical property and works as a hole-transport layer in a double-layer electroluminescence cell emitting -500nm light. The crystallinity of CuPc thin films was improved by heating a substrate at -320K during the deposition or by irradiating the film surface with He-Ne laser at room temperature.

Enhancement of the NO 2-sensing capability of copper phthalocyanine by measuring the realtive resistance change

The gas-sensing properties of copper phthalocyanine (CuPc) thin films have been measured for NO 2 concentrations of 1 to 10 parts per million (ppm). The CuPc films thermally evaporated on glass substrates appear to have an α-form polycrystalline structure. Most measurements of gas sensitivity are done with heat-cleaned sensing elements to reduce the instability of CuPc resistance. We have established unambiguously that a significant enhancement of detectivity can be accomplished by converting the resistance to a normalized figure, i.e., the relative resistance. Good sensitivity to as low as 1 ppm has been reproducibly achieved.

Simultaneous Analysis of Total Reflection X-Ray Diffraction and Fluorescence from Copper-Phthalocyanine Thin Films during Evaporation Process

A newly developed X-ray measuring system, capable of simultaneously conducting total-reflection X-ray diffraction (TXRD) and total-reflection X-ray fluorescence (TXRF) analyses, was utilized to follow the adsorption and structural changes in copper phthalocyanine (CuPc) thin films during an evaporation process. The intensities of Cu Kα fluorescent X-rays provided precise data on the amount of CuPc molecules adsorbed on the substrate of SiO2, and thus the difference in adsorption coefficient of CuPc molecules on the SiO2 substrate and the oscillator surfaces of Ag could be evaluated in the first place. Moreover, by combining these fluorescent data with the diffraction data we could follow the exact changes of molecular orientation with the increase of film thickness. The data on the film thickness variations of the X-ray profiles revealed that the structural change in the CuPc molecular crystal occurred at about 9 nm thickness of the evaporated film.

95/06205 Enhancement of the photovoltaic conversion efficiency of copper phthalocyanine thin film devices by incorporation of metal clusters

95/06205 Enhancement of the photovoltaic conversion efficiency of copper phthalocyanine thin film devices by incorporation of metal clusters

Enhancement of the photovoltaic conversion efficiency of copper phthalocyanine thin film devices by incorporation of metal clusters

ITO-copperphthalocyanine-indium sandwich structures have been prepared by thermal evaporation in high vacuum. Different types of metal nanoclusters have been incorporated at the ITO-copperphthalocyanine interface. Significant differences in the photovoltaic conversion efficiency of the sandwich samples have been established as a function of the excitation wavelength. Copper clusters have been found to increase the conversion efficiency by a factor of nearly three for solar illumination. The observed effects are discussed assuming resonant light absorption in the metal clusters as the responsible physical mechanism for enhancement.

Electrical conductivity studies and optical absorption studies in copper phthalocyanine thin films

The electrical conductivity and optical properties of copper phthalocyanine thin films have been measured. Films used in the characterisation studies are vacuum evaporated. Electrical measurements were done using a programmable Keithley electrometer model 617. The data has been analysed to obtain the activation energy. The ultra-violet visible range spectrum is analysed to obtain the transition energy gap.

Surface enhanced Raman scattering on silver grating: Optimized antennalike gain of the stokes signal of 104

Using a silver grating of variable groove depth overcoated by a thin film of copper phthalocyanine, we measured an increase of the Raman efficiency of 104 as compared to the flat case (copper phthalocyanine on a flat silver surface). This effect is due to the resonant excitation of delocalized surface plasmons. The value of 104 corresponds to an optimum groove depth of the grating which acts as a high gain directive antenna when surface plasmons resonance is achieved at the Stokes frequency.

Identification of two-photon states in phthalocyanines by third harmonic generation spectroscopy

The dispersive behaviour of the magnitude and phase of χ 3(−3 ω; ω, ω, ω) of sublimated metal-free (PcH 2) and copper phthalocyanine (PcCu) thin films has been investigated via third harmonic generation (THG) spectroscopy in the range of 950 to 2000 nm. A two-photon state placed at around 500 nm, between the two one-photon allowed levels, has been identified and correlated with transitions from the a u to the b 1u ∗ levels. In PcCu an additional two-photon state located at the lower energy side of the Q band, likely associated with a d-d transition, has also been inferred from the spectrum.

The molecular orientation in copper phthalocyanine thin films deposited on metal film surfaces

The molecular orientation in copper phthalocyanine (CuPc) films deposited on metal films of Au, Ag, Cu and Cr has been studied by reflection-absorption infrared spectroscopy and X-ray diffraction. The molecular planes of CuPc in the ultra-thin films (corresponding to several tens of monolayers) deposited on Au, Ag and Cu films were found to be nearly parallel to the metal film surfaces. Further deposition (up to 100 nm) on such thin films produces a molecular orientation with the molecular planes inclined away from the metal film surfaces. This corresponds to a crystal structure of the α phase with a standing b axis configuration. However, the molecular planes of the CuPc deposited on Cr films are rather perpendicular to the Cr film surfaces. These CuPc films are in the α phase with a parallel b axis configuration.

Optical recording using copper phthalocyanine thin films

Optical recording using copper phthalocyanine thin films

Copper phthalocyanine film studied with spectroscopic ellipsometry

The ellipsometric spectra of vacuum sublimed copper phthalocyanine (CuPc) thin film on single-crystal silicon were studied on a new type of scanning ellipsometer with the analyser and polarizer rotate synchronously. The electronic structure of the spectra is discussed.

Formation and characterization of epitaxial phthalocyanine and perylene monolayers and bilayers on Cu(100): Low-energy electron diffraction and thermal desorption mass spectrometry studies

Ordered monolayer and multilayer thin films of copper phthalocyanine (CuPc) and perylene dicarboxylic dianhydride (PTCDA) have been grown on Cu(100) single crystals. CuPc grows in a commensurate square lattice configuration, with two equivalent domains consisting of closest packed, flat lying Pc rings, rotated at ±21.8° from the principle Cu(100) axes. The dimensions of these square lattices (b1=b2=13.7 Å) are comparable to those observed using other substrates which interact weakly with the Pc overlayer (layered metal dichalocogenides, cleavage faces of single-crystal salts). PTCDA grows in a commensurate rectangular lattice (5√2×4√2)-R=45°, whose dimensions (b1=14.5 Å, b2=18.1 Å) are significantly different than those seen on weakly interacting substrates. Low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy, and thermal desorption mass spectroscopy (TDMS) data for the adsorption of this molecule strongly suggest that the first monolayer is dissociatively adsorbed to the Cu(100) surface. Growth of ordered layers of PTCDA has also been carried out on a Cu(100) surface modified with 1–2 ML (monolayers) of an ordered CuPc film. LEED and TDMS data indicate the formation of a new commensurate rectangular unit cell (b1=13.7 Å, b2=20.5 Å) for these PTCDA/CuPc/Cu(100) overlayers, which suggest that the CuPc layer controls the architecture of the subsequent PTCDA layers. The formation of a wide range of highly ordered organic heterojunctions appears to be possible, starting with a strongly adsorbed first layer, on surfaces such as single-crystal metals.

Gas sensitivity of phthalocyanine thin films

Thin films of copper phthalocyanine (CuPc) and poly(phthalocyanine of aluminium and fluor) (AlPcF) n were exposed to concentration steps of the diluted oxidizing gases O 2, NO 2 and Cl 2, and their conductivity variations were recorded at the same time. These are in good agreement with the model we recently proposed to describe gas-phthalocyanine interactions, leading to the law: (conductivity)α(gas concentration) s , which is often experimentally observed. The sensitivities s of the two phthalocyanines to O 2 and NO 2 are calculated at various temperatures.

Second-harmonic generation in thin films of copper phthalocyanine.

We have observed the optical second-harmonic generation (SHG) from a polycrystalline film of copper phthalocyanine (CuPc) with thicknesses between 40 and 2000 K. The nonlinear susceptibility of this film is χ ZYY (2) =1.89×(3/4π)×10 -7 esu where Z and Y are the directions perpendicular and parallel to the film surface, respectively. This value is unexpectedly large, approaching a quarter of the value for the well-known nonlinear optical crystal LiNbO 3 . The finite value of the nonlinear susceptibility indicates that the structure of this film lacks inversion symmetry. The polarisation properties of the second-harmonic (SH) light show that the film lacks inversion symmetry perpendicular to the film surface

Direct observation of an organic superlattice structure.

Organic multilayered thin films of copper phthalocyanine (CuPc) and naphthalene-1,4,5,8-tetracarboxylic-1,8:4,5-dianhydride were fabricated by an organic molecular beam deposition technique. The analyses by an x-ray photoelectron spectroscopy and a transmission electron microscopy directly revealed an alternating layer-by-layer structure, with a few nanometers thickness for each layer. The optical absorption spectra at the Q band for CuPc layers indicates an extraordinary electronic state in an organic superlattice structure.