Adirek Rangkasikorn

Growth and characterizations of tin doped zinc-phthalocyanine prepared by thermal co-evaporation in high vacuum as a nanomaterial

This research is related to the growth and characterizations of the novel hybrid nanomaterial, tin doped zinc-phthalocyanine thin films (Sn-doped ZnPC), grown by thermal co-evaporation. The concentration of Sn in hybrid films was controlled by adjusting the deposition rate between Sn and ZnPc. The hybrid films were characterized by atomic force microscopy and UV–visible spectroscopy to reveal the physical and optical properties of hybrid films. Moreover, the electrical properties, e.g., carrier mobility and carrier concentration, of the indium tin oxide (ITO)/Sn-doped ZnPc/aluminium (Al) devices were extracted from the current–voltage and capacitance–voltage characteristics. Furthermore, X-ray photoelectron spectroscopy and Raman spectroscopy was employed to explore the chemical interaction taking place in doped films. Sn doping into ZnPc changes the films specific properties, e.g., morphology, crystalline packing, absorption spectra, and conductivity. Moreover, no chemical bond is formed between Sn and ZnPc, and Sn dopants are formed as metal clusters covered by derivative oxide (SnOx) embedded in the Sn-doped ZnPc film.

Study on Optical and Electrical Properties of Bismuth-Doped Nickel-Phthalocyanine Thin Films

The objective of this work is to investigate the optical and electrical properties of bismuth-doped nickel-phthalocyanine thin films (Bi-doped NiPc). The doped films were prepared by thermal co-evaporation as a function of Bi concentration. The amount of Bi in NiPc was controlled via different deposition rates between metal dopant and organic host. The optical properties of the hybrid films were characterized by spectroscopic techniques. Furthermore, the electrical properties e.g. charge carrier concentration and carrier mobility of Al/Bi-doped-NiPc/ITO devices were characterized by current-voltage and capacitance-voltage measurements. The results of optical properties suggest that the crystalline packing of NiPc molecules in all preparation conditions is a combination of α-phase (majority) and β-phase (minority). However, the evolution of β-phase NiPc is observed with the increase of metal doping concentration. Raman spectroscopic results reveal that there is no chemical bond taken place between Bi and NiPc. In addition, with increasing dopant concentration, electrical properties present the enhancement of conducting current of hybrid devices as result from the increment of both charge carrier concentration and charge carrier mobility.

Study of Optical and Electrical Properties of Tin-Doped Magnesium Phthalocyanine Thin Films Grown by Thermal Co-Evaporation

The aim of this work is to investigate specific properties of tin-doped magnesium phthalocyanine (Sn-doped MgPc) thin films grown by thermal co-evaporation. Morphological, optical and chemical properties of the doped-films were characterized by atomic force microscopy (AFM), UV-Visible spectroscopy and X-ray photoelectron spectroscopy (XPS). Furthermore, electrical properties of ITO/Sn-doped-MgPc/Al devices such as carrier mobility and carrier concentration were extracted from current-voltage and capacitance-voltage measurements. Morphology of the doped films shows strong dependence on the existence of Sn in the doped films as clearly observed by changing of features of the film surface e.g. surface grain size and roughness. Optical absorption spectra of all conditions provide regular three dominant beta-phase peaks at 352, 640 and 691 nm corresponding to absorption from B-band and Q-band, respectively. The electrical properties obtained from ITO/Sn-doped MgPc/Al device suggest that the enhancement of the current flow in the doped device is a result from the increase of both carrier mobility and carrier concentration. Moreover, photoelectron analysis reveals two formations of Sn dopant in MgPc those are tin metal and derivative of tin oxide.

Hole Doping Through Indium Intercalation Into Nickel Phthalocyanine

A new intercalation of indium and nickel phthalocyanine(NiPc) thin films is developed by using thermal co-evaporation technique. X-ray diffractometer(XRD) and optical absorption spectroscopy of In-doped NiPc suggest the crystal structure of In-doped NiPc is α-phase as same as that of pristine NiPc. Current-voltage characteristic of Shottky diode fabricated with In-doped NiPc thin film shows the enhancement of charge carrier concentration due to indium doping. Further photoelectron spectroscopy experiments prove that In-doped NiPc is hole transport material.

Exciton Dissociation at Indium Tin Oxide/Indium Doped Zinc Phthalocyanine Interface

A new intercalation of Indium and zinc phthalocyanine(ZnPc) thin film is developed by using thermal co-evaporation technique. The exciton dissociation at the interface of Indium Tin Oxide(ITO) electrode and Indium doped ZnPc upon laser irradiation is observed through the transient photovoltage measurement technique in comparison with the interfacial exciton dissociation occurred at ITO/pristine ZnPc interface. The occurring transient photovoltage spike is regarded as the effect of exciton dissociation at ITO/In-doped ZnPc interface and depends on the amount of free carrier separation by built-in field or charge carrier concentration according to doping ratio. The experiments demonstrate the existence of exciton dissociation at ITO/In-doped ZnPc interface, the direction of charges transfer is that holes are injected to ITO, whereas electrons are left in bulk film. A thin insulating layer of 6 nm thick lithium fluoride(LiF) is inserted between ITO and In-doped ZnPc to prevent the exciton dissociation at ITO/In-doped ZnPc interface and insist on the phenomenon of interfacial exciton dissociation. Further photoelectron spectroscopy experiments prove that In-doped ZnPc is hole transport material.

Evidence of Phase Transition of Indium Doped Zinc Phthalocyanine

A new intercalation of Indium and Zinc Phthalocyanine(ZnPc) thin films is developed by using thermal co-evaporation method. Optical characteristics of In-doped ZnPc are studied in comparison with pristine ZnPc, which shows improvement on optical absorption at the visible spectrum. The presence of a new phase transition upon Indium doping is examined and consequently support the idea of the intercalated phase upon doping. A Schottky diode made of Indium doped ZnPc is fabricated in order to measure its electrical properties, its photo-current spectrum confirms the existence of phase transition.

XPS Investigation of an Increasing C-H Vibration of Pentacene Doped with Indium

We investigate the increase of C-H vibration in benzene rings of pentacene molecule upon doping with indium by the X-ray photoelectron spectroscopy (XPS) characterization technique. The risen of C-H vibration spectral component is employed to demonstrate the charge transfer between In dopant atoms and C atoms in benzene rings of pentacene molecule. This experiment can be used to explain the same mechanism of charge transfer between In dopant atoms and C atoms in In-doped nickel-phthalocyanine(NiPc).

The Effect of the Central Metal Atom on the Structural Phase Transition of Indium Doped Metal Phthalocyanine

We investigate the effect of central metal atom on the phthalocyanine (Pc) molecular crystals as intercalated with indium. As dopant, indium has physical interaction with some atom in the ring of Pc molecule and there is charge transfer between indium atom and Pc ring atom. Since In-doped Pc is a hole doping which increase positive charge carriers and the HOMO of ZnPc, CuPc, NiPc and MgPc are localized on the phthalocyanine ring, then, the central metal atom e.g. Zn, Cu, Ni and Mg are not directly involved with the charge transfer between indium dopant and their Pc molecule. The structural phase transition from α phase to β phase of ZnPc upon doping with indium is another evidence for the existing of charge transfer between dopant atom and matrix Pc molecule. A comparative experiment of optical absorption spectrum of each metal Pc reveals that the central metal atom will affect the forming of crystal structure whether will be α phase or β phase as intercalated with indium.

Study on Optical and Electronic Properties of Sn-Doped ZnPc

Sn doped ZnPc films were deposited on intrinsic Si and glass substrates by organic source thermal co-evaporation technique with different deposition rates. Optical properties and electronic structure were characterized by UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) respectively. The UV-Vis results showed that phase transition of ZnPc from α-phase to β-phase occurred when Sn:ZnPc deposition rate is 0.3:0.7 or higher. XPS results indicated that the outer s electron of Sn atom is transferred to the ZnPc. Broadening of the C 1s spectra is observed with the increasing of Sn deposition rate. This broadening corresponds to the change of molecular environment surrounding carbon atoms in the Sn-doped ZnPc films.

Hole Doping Through Indium Intercalation into Copper Phthalocyanine

A blend of molecular acceptor and molecular donor made of Copper Phthalocyanine (CuPc) and Indium in various ratios were evaporated in high vacuum on to intrinsic silicon substrates by using vacuum thermal co-evaporation technique. Electronic properties of In-doped CuPc thin films have been examined by X-ray photoelectron spectroscopy (XPS). The results obtained by XPS suggests that In-doped CuPc is a hole transport material.