MgPc Thin Films Research Articles

Physical Properties Studies of Magnesium Phthalocyanine (MgPc) Thin Films of Different Annealing Temperatures Prepared by Pulsed Laser Deposition Technique

Magnesium Phthalocyanine (MgPc) was deposited on a glass substrate by pulsed laser deposition (PLD) using Q-Switching Nd:YAG laser with wavelength 1064 nm, repetition rate 6 Hz, at room temperature (300K) and different annealing temperatures (373, 473, and 573)K under vacuum condition of 10-3 torr. All films were annealed for one hour to attain crystallinity. X-ray diffraction (XRD) of MgPc powder indicated that MgPc crystallizes in polycrystalline with a monoclinic structure. While comparing the MgPc films, it was observed that the intensity of the characteristic peak increases with temperature, and the crystallization exhibited a monoclinic structure typical of the β-form. The Miller indices, hkl, values for each diffraction peak in the XRD spectrum were calculated. The characteristic peak of Phthalocyanine (MgPc) was found at 2θ value 6.9137ᵒ with the hkl value of (100) for both MgPc powder and deposited thin films. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) analyses indicated that crystallinity improved and surface morphology was enhanced with the rise in annealing temperature and showed uniform-sized grains. They also assisted in identifying the optimal parameters that yielded the best structural properties for the film. The optical properties of MgPc thin film showed two absorption bands. The MgPc thin films exhibit transport and onset direct energy gaps (Eg) for all samples. Additionally, the absorption coefficient (α) was calculated using Lambert Law, revealing a slight dependence on the annealing temperature.

Investigation of structural, electrical and linear/non-linear optical properties of MgPc thin films grown by CSP technique for optoelectronic applications

Investigation of structural, electrical and linear/non-linear optical properties of MgPc thin films grown by CSP technique for optoelectronic applications

Effect of gamma irradiation on the optical properties of nano-MgPc thin films

The thermal evaporation technique was used to deposit MgPc thin films. XRD and TEM studies were carried out for MgPc thin films. The effects of γ-radiation on the optical properties of MgPc thin films were characterised by using spectrophotometric measurements of the transmittance and reflectance in the spectral range from 200 nm to 2500 nm. The absorption spectra recorded in the UV-Vis region for as-deposited and radiated films showed two well-defined absorption bands of phthalocyanine molecule, namely the Q-band and the Soret (B) band. The Q-band showed its characteristic splitting (Davydov splitting) and ΔQ was obtained as 0.17 eV. The refractive index, n and the absorption index, k, were calculated. According to the analysis of dispersion curves, the parameters, namely; the dispersion energy (Ed), the oscillator energy (E0) and the dielectric constant at infinite wavelength e∞. Some of the important optical absorption parameters such as the molar extinction coefficient (e molar ), the oscillator strength, (f) and the electric dipole strength (q2 ) of the principle optical transitions were evaluated. The analysis of the spectral behaviour of the absorption coefficient (α), in the absorption region revealed indirect transitions. The optical and the onset respectively energy gaps were estimated as 2.74 and 1.33.

Structural and optical properties of thermal evaporated magnesium phthalocyanine (MgPc) thin films

X-ray powder diffraction (XRD) of MgPc indicated that the material in the powder form is polycrystalline with monoclinic structure. Miller indices, h k l, values for each diffraction peak in XRD spectrum were calculated. Thermal evaporation technique was used to deposit MgPc thin films. The XRD studies were carried out for MgPc thin films where the results confirm the amorphous nature for the as-deposited films. While, polycrystalline films orientated preferentially to (1 0 0) plane with an amorphous background were obtained for films annealed at 623 K for 3 h. Optical properties of MgPc thin films were characterised by using spectrophotometric measurements of transmittance and reflectance in the spectral range from 190 to 2500 nm. The refractive index, n, and the absorption index, k, were calculated. According to the analysis of dispersion curves, the parameters, namely; the optical absorption coefficient ( α), molar extinction coefficient ( ɛ molar), oscillator energy ( E os), oscillator strength ( f), and electric dipole strength ( q 2) were also evaluated. The recorded absorption measurements in the UV–vis region show two well defined absorption bands of phthalocyanine molecule; namely the Q-band and the Soret (B-band). The Q-band showed its splitting characteristic (Davydov splitting), and Δ Q was obtained as 0.15 eV. The analysis of the spectral behaviour of the absorption coefficient ( α), in the absorption region revealed indirect transitions. The transport and the near onset energy gaps were estimated as respectively 2.74 ± 0.02 and 1.34 ± 0.01 eV.

Chlorine gas sensors with high sensitivity using Mg-phthalocyanine thin films

High sensitivity chlorine (Cl 2) gas detection has been realized by newly developed gas sensors using Mg-phthalocyanine (MgPc) thin films. The MgPc thin film gas sensors exhibited an increase of conductivity with exposure to Cl 2 gas. The sensing properties of the MgPc thin film gas sensors were strongly dependent on the preparation conditions of MgPc thin films. The highest sensitivity for Cl 2 gas was obtained in the gas sensor using MgPc thin film prepared under the optimized preparation conditions; substrate temperature of 180 °C, evaporation temperature of 475 °C and film thickness of 40 nm. It was obtained that at operating temperature of 200 °C, the sensitivity of the MgPc thin film gas sensor linearly increased with the Cl 2 gas concentration in the range of 0.18–35 ppm.

Effect of air annealing on the electrical and optical properties of MgPc thin films

Electrical and optical properties of thermally evaporated air-annealed magnesium phthalocyanine (MgPc) thin films are studied. Thermal activation energy is calculated from the Arrhenius plot and in the intrinsic region, it is found to increase with the temperature up to 200 °C and decreases to a low value at 250 °C. Narrowing of band gap is observed with annealing temperature.

Dark and photoelectric conversion properties of p-MgPc/n-Si (Organic/Inorganic) heterojunction cells.

Heterojunction cells of p-MgPc/n-Si have been fabricated by thermal evaporation of MgPc thin films onto Si〈100〉 single crystal wafers. The devices exhibit strong photovoltaic characteristics with an open–circuit voltage of 0.35 V, a short–circuit current of 3.57 mA and a power conversion efficiency of 1.05%. These parameters have been estimated at room temperature and under a monochromatic illumination of 633 nm with an input power density of 50 mW/cm 2. The activation energy of the charge carriers of 0.32 eV and the cell series resistance of 2 kΩ have been evaluated from the measurements of the dark I– V characteristics. A free–carrier concentration of 2.2×10 16 cm −3 and a barrier width of 75 nm have been estimated from C– V measurements. The temperature dependence of photocurrent, at constant illumination, has been also investigated.