Jun'ichiro Muto

Electrodeposition and properties of copper-doped cadmium sulphide

Abstract Thin films of copper-doped CdS were co-electrodeposited (in situ doping) galvanostatically onto indium tin oxide coated glass substrates using dimethylsulphoxide solutions at 120°C containing cadmium chloride, elemental sulphur and copper (II) chloride. The doped crystals were characterized structurally based on X-ray diffraction, scanning electron microscopy and Auger electron spectroscopy analysis. The photoconductive and optical properties of the co-deposited films were also examined. At a Cu concentration in the solution of below 5 × 10−4 M, the grown films show good quality, while for [Cu] ⩾ 10−3 M there is poor adhesion to the substrate and an amorphous-like structure.

Growth and characterization of 70Gen/74Gen isotope superlattices

Abstract We report on the molecular beam epitaxial (MBE) growth of 70 Ge n / 74 Ge n isotope superlattices composed of alternating layers of the stable isotopes 70 Ge and 74 Ge. Samples prepared in this work have atomic layers n =4, 8, 16, and 32. All superlattices are p-type having a net-impurity concentration of ∼10 16 cm −3 . Zone-folding of optical phonons due to the mass periodicity in the growth direction has been observed clearly for all samples using high resolution Raman spectroscopy. The corresponding phonon mode of each Raman peak has been indexed according to theoretical calculations using the linear-chain model and the planar bond-charge model. The frequency of the Raman peaks found by the experiment agree very well with those of the phonon modes calculated for each superlattice structure. A detailed analysis of the Raman spectra concludes that the degree of interface mixing between 70 Ge and 74 Ge layers for our typical growth condition is less than two monolayers.

Preparation and properties of electrodeposited ternary CdSxSe1-x and ZnxCd1-xS films

Abstract Mixed CdS-CdSe and ZnS-CdS films were electrodeposited cathodically onto indium tin oxide substrates from dimethylsulphoxide solutions at 120°C containing cadmium chloride, elemental sulphur, and elemental selenium or zinc chloride. The mixed crystals were characterized structurally based on X-ray diffraction and scanning electron microscopy analyses. The optical absorption and the photoconductive properties of the mixed films were also examined. It is found that the band gap of the films can be varied between 2.1 and 2.8 eV by changing the composition of the deposition solution.

Preparation and characterization of pulse-plating electrodeposited CuInSe2 thin films

CuInSe2 thin films were electrodeposited on an indium-tin-oxide glass substrate by a pulse-plating technique from an aqueous electrolyte solution, containing CuSO4, InCl3 and SeO2 with the pH adjusted to 1.5 at room temperature. The deposited and heat-treated films were characterized structurally using X-ray diffraction (XRD), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) analysis. The optical and the electrical properties of the films were also examined. When the film was submitted to heat-treatment above 300 ‡C in air for 1 h, the sample showed a chalcopyrite structure and n-type conductivity with a carrier concentration of ~ 1017 cm−3 and a band-gap (direct allowed transition) energy of 0.99 eV.

Thermal bleaching of rhodamine 6G in polymethyl methacrylate (PMMA)

Abstract Thermal bleaching of rhodamine 6G in PMMA is investigated at temperatures between 65°C and 83°C with a heating time of over 300 hours. The obtained thermal bleaching rate is found to show a sudden change around 70°C.

Concentration dependent laser threshold of rhodamine 6G in methanol solution

Abstract We have examined a dye concentration dependent laser threshold for rhodamine 6G in methanol under weak N 2 laser excitation (337 nm), between 5 x 10 -4 and 1.5 x 10 -2 . The results are analysed with consideration of the penetration dependent diffraction loss in the resonator. The behaviour of the threshold exciting intensity of rhodamine 6G in methanol against concentration pumped by a 530 nm light source is also discussed.

On the photobleaching quantum yields of heat-treated rhodamine 6G (Rh6G) molecules in the copolymer of methyl methacrylate (MMA) with methacrylic acid (MA)

Abstract An analysis is presented to explain photobleaching of heat-treated Rh6G/P (MMA + MA) in which photo product as well as two types of dye molecules with different quantum yields for photodegradation are taken into account. It is found that the values of the above two quantum yields for photobleaching remain unchanged, while a fraction of the molecules with higher quantum efficiency decreases with heat treatment time.

Diffusion of alcohol-rhodamine 6G in polymethyl methacrylate

Rhodamine 6G (Rh6G) is impregnated in polymethyl methacrylate by concentration difference diffusion method. The diffusion behaviour of ethanoic and methanoic Rh6G in polymethyl methacrylate at temperatures between 35 and 70° C were studied. The following results were obtained: (a) Visually observed sharp boundary, characteristic of Case II transport, during diffusion of alcohol penetrates at a rate of 1.7×10−6 cm sec−1 with an activation energy of 23 kcal mol−1 for ethanol-polymethyl methacrylate system and 1.0×10−5 cm sec−1, with 23 kcal mol−1 for methanol-polymethyl methacrylate, respectively, at 60° C. (b) Diffusion of alcoholic Rh6G in polymethyl methacrylate is greatly hindered since internal stresses exist in the swollen region of the glassy polymer. (c) Diffusion of alcoholic Rh6G in swollen polymethyl methacrylate with equilibrium alcohol concentration followed Fickian kinetics. The diffusion coefficient of Rh6G at 60° C is determined as 5.2×10−8 cm2 sec−1 with an activation energy of 41 kcal mol−1 for the wet ethanol-polymethyl methacrylate and 6.1×10−8 cm2 sec−1, with 34 kcal mol−1 for the wet methanol-polymethyl methacrylate systems, respectively.

Properties of μm-thick CdSe prepared by vacuum deposition

We have fabricated vacuum-evaporated CdSe films with thickness, of the order of micrometers. The films show hexagonal structure with c-axes perpendicular to the glass substrates. At higher temperatures, the sample exhibits grain-boundary scattering and Se the vacancy acts as a donor impurity; while at lower temperatures, shallow donor levels overlap into the conduction band and thus metallic impurity conduction occurs.

Electrical and structural properties of ortho-chloranil doped zinc phthalocyanine films

Electrical conductivity of evaporated zinc phthalocyanine (ZnPc) films, doped with orthochloranil (o-CA) molecules, is investigated. Benzoico-CA solution is introduced in the film and benzene is removed by vapourization afterwards. The film conductivity at first increased and then decreased with incremental doping. The maximum conductivity of the sample appeared at doping level × (=o-CA/ZnPc) ≈ 0.2 and is about 103 times as large as that of the as-evaporated one. About a ten-fold further increase in the conductivity is obtained by the heat-treatment of 150 °C for 12 h. The conductivity change by doping is explained by taking into account thato-CA molecules behave not only as acceptors in the film but destructively for the film structure. The phase change of ZnPc by benzoic solution is also discussed.