Photo-induced structural disorder in Langmuir-Blodgett films of polydiacetylenes

Molecular vibration spectra were measured on Langmuir-Blodgett films of polydiacetylene, PDA-(12, 8), by the grazing-incidence reflection method. Structural disorders in the side-group conformation were found to occur at photo-induced phase-transition in the polymer backbone structure.     

An XPS study of hafnium nitride films

XPS spectra are presented from films of different stoichiometry: HfN_1.0 made by CVD and reactive sputtering and HfN_1.09 made by ion plating. They support the existing theoretical calculations where the valence band comprises a strong Hf 5d band immediately below E_F and a band of mainly N 2p character some 6 eV below E_F. The core levels are shifted to larger binding energies by about 1.5 eV indicating electron transfer from hafnium to nitrogen. The effect of substoichiometry on the spectra is very small.     

LB膜的XPS光谱及其电致发光

采用X射线光电子能谱 (XPS)和UV Vis光谱研究了 2个以 8 氨基喹啉为亲水头基的两亲配体 ;2 长链烷基丙二酸二 (8 氨基喹啉 )酰胺 (H2 A) (H2 A1 2 :长链烷基为十二烷基 ;H2 A1 6 :十六烷基 )在气 /水界面与Cu2 离子的配位作用。配位后H2 A1 2 和H2 A1 6 单分子膜的崩溃压分别由 12 5和 15 6mN·m- 1 增加至 2 8 0和33 8mN·m- 1 。从含Cu2 离子亚相表面组装的LB膜出现了Cu2 离子的特征XPS峰 ,Cu2p为 935和 95 5eV ,XPS表明H2 A与Cu2 的配位比为 1∶1。H2 A的LB膜可以用作电致发光 (EL)器件的空穴传输材料 ,三层EL器件ITO/TPD/LB膜 /Alq3/Al(LB膜分别为 15层H2 A1 2 和 15层H2 A1 6 )的驱动电压分别为 6 5和 7 5V ,最大亮度分别为 6 2 1和 2 0 1cd·m- 2 。     

Liquid-crystal alignment of phthalocyanine-derived Langmuir-Blodgett films

Twisted nematic liquid crystals were uniformly aligned on Phthalocyanine (Pc)-derived Langmuir-Blodgett (LB) films. By scanning tunneling microscopy imaging, it was found that the Pc-LB film has a well-ordered in-plane column-like structure oriented in the dipping direction, based on which the alignment mechanisms are discussed.     

Glass transition of Langmuir-Blodgett polymer films

The dielectric dispersion of vinylidene fluoride-trifluoroethylene copolymer P(VDF/TrFE) (70/30) films obtained by the Langmuir-Blodgett technique was investigated in the low-temperature range from 20 to −100°C. The thickness of the explored films was 40 nm. A glass-transition range from −25 to −40°C was detected; this indicates the presence of an amorphous phase in the LB films.     

Activation of Zr-Co-rare earth getter films: An XPS study

Thin films of non-evaporable getters are employed in the field of electronic devices packaging, as they provide a simple and effective solution for pumping in sealed applications. In particular thin films of Zr-Co-rare earth alloys deposited by sputtering have been developed for this purpose and successfully employed in industrial applications. In this paper we present an X-ray photoelectron spectroscopy investigation of the effect of thermal activation of the getter from the point of view of the induced surface chemical modification as seen by such a surface sensitive technique. We find that the activation process reflects in a clear reduction of Zr, accompanied by a decrease of the oxygen concentration at surface, which is fully accomplished already at 350 °C; while at 450 °C there is a significant increase of the cobalt concentration at surface.     

Dielectric dispersion in Langmuir-Blodgett ferroelectric polymer films

The dynamic permittivity of vinylidene fluoride-trifluoroethylene (70:30) copolymer films is measured over wide ranges of frequencies and temperatures. It is revealed that 15-to 45-nm-thick Langmuir-Blodgett films of the vinylidene fluoride-trifluoroethylene copolymer undergo a Debye-type dielectric relaxation. The relaxation time τ increases as the temperature increases and the ferroelectric phase transition is approached. This effect is interpreted as a result of critical slowing down. The influence of gamma irradiation on the dielectric response of Langmuir-Blodgett films consisting of 10 and 30 monolayers is investigated.     

Study of the structural features of skeletonized Langmuir-Blodgett films by means of volume-acoustic-wave and surface-acoustic-wave devices

Langmuir-Blodgett films made from 1.3-diketones of metals are studied by the microbalance and surface-acoustic-wave methods and by ellipsometry. It is shown that parallel studies of this kind, taken together with measurements of the surface density and resistivity of the films, permit an integrated estimate of their elastic properties. It is found that skeletonization leads to an increase in their structural stiffness and volume density. Zh. Tekh. Fiz. 67, 72–75 (February 1997)     

A Mössbauer spectroscopy study of antiferromagnetic iron arachidate Langmuir-Blodgett films

Langmuir-Blodgett multilayers of ferric arachidate (abbreviated: FeA) on silicon wafers have been investigated by means of conversion electron Mössbauer spectroscopy (CEMS) and absorption Mössbauer spectroscopy at different temperatures between room temperature and 4.2 K, without and with external magnetic fields up to 5 T. The films show a quasicrystalline structure with ac-axis orientation perpendicular to the plane and a random distribution of orientations in the plane of the films. All Mössbauer spectra show Fe³⁺. At low temperatures, antiferromagnetic ordering has been observed. The lines in both the room temperature and the low-temperature spectra are significantly broadened, which is due to a distribution of electric field gradients and hyperfine fields. The reason for this is a slightly disordered iron environment. The orientation and the distribution function of the internal magnetic fields have been determined.     

Langmuir-Blodgett films of hydrophobins HFBI and HFBII

Hydrophobins are small fungal proteins, which have remarkable surface-chemical properties. They self-assemble at hydrophobic/hydrophilic interfaces and work as adhesive agents and coatings. Sixteen layer Langmuir-Blodgett films of hydrophobins HFBI and HFBII from the fungus Trichoderma reesei were prepared and studied using grazing-incidence X-ray diffraction and reflectivity techniques. Both kind of films contain hexagonally ordered crystallites on the substrate with unit cell parameters of a = b = 54 Å (HFBI) and a = b = 55 Å (HFBII). The structure is similar to the structure of monolayer Langmuir-Blodgett films.     

Dielectric dispersion of ultrathin polymer Langmuir-Blodgett films

Dielectric dispersion is studied in films made of vinylidene fluoride/trifluoroethylene copolymer [P(VDF/TrFE)], which are obtained by the Langmuir-Blodgett technique in the temperature range from −90 to +132°C. The thickness of the films studied is ∼7 nm. A glass transition is observed in the temperature range from −40 to −50°C; this indicates the presence of an amorphous phase in the ultrathin Langmuir-Blodgett films.     

AFM studies on Langmuir-Blodgett films of cholesterol

The Langmuir monolayer of cholesterol at the air-water interface exhibits a condensed phase in which the cholesterol molecules are aligned normal to the water surface. We have transferred the monolayer from water surface to different substrates by Langmuir-Blodgett (LB) technique and have studied their assembly by atomic force microscope (AFM). Our studies reveal that the aggregation of cholesterol molecules on hydrophobic surfaces leads to interesting structures. The cholesterol molecules assemble into a uniform film, elongated domains and uniformly distributed torus-shaped domains (doughnuts) for one, two and four cycles of deposition, respectively. Beyond four cycles, the molecules adsorb and desorb by an equal amount resulting in no further deposition. The formation of uniformly distributed doughnuts can be attributed to the hydrophobic interaction and reorganization of the molecules due to successive adsorption and desorption during deposition cycles. Our studies on hydrophilic surfaces show that cholesterol cannot form more than one layer of deposition.PACS: 68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces - 68.37.Ps Atomic force microscopy (AFM) - 68.43.Mn Adsorption/desorption kinetics     

Kinetics of long-lived luminescence of eosin in Langmuir-Blodgett films

The spectral and kinetic properties of photoluminescence of mixed Langmuir-Blodgett (LB) films of eosin decyl ether and palmitic acid on a solid substrate are studied. The electronic absorption and fluorescence spectra of the films are identical to the spectra of the dye in ethanol. An increase in the dye concentration in a monolayer results in the appearance of a dimer absorption band, quenching of fluorescence of monomers, and the red shift of the spectral bands. At 90 K, the distinct phosphorescence and delayed fluorescence bands of LB films were observed. The decay kinetics of phosphorescence and delayed fluorescence is nonexponential. It is shown that the decay curve of delayed fluorescence is determined by triplet-triplet annihilation (TTA) and T ₁→S₁ triplet-singlet intersystem crossing (IS). The initial nonexponential phosphorescence decay is caused the dominant contribution of TTA to the decay of triplet molecules. The experimental data are interpreted based on the mechanisms of exchange-resonance and inductive-resonance annihilation.     

Ferroelectric phase transition in Langmuir-Blodgett films of copper phthalocyanine

A ferroelectric phase transition is observed in Langmuir-Blodgett films prepared from substituted copper phthalocyanine molecules. The linear and nonlinear dielectric properties of the films and the switching of their spontaneous polarization are investigated in the temperature range of the phase transition. The observed features can be explained by the Landau-Ginzburg model of a first-order phase transition. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 9, 625–631 (10 November 1999)     

紫膜LB膜中的光学相位共轭研究

首次报道了在纯紫膜LB膜中实现光学相位共轭输出的实验现象,并在理论上从简化的菌紫质分子光循环模出发,导出了共轭光强度与总入射光强度之间的关系,最后用拟合方法求得这种紫膜LB膜的饱和吸收强度为0.49W/cm~2,bR分子处于中间体M(410)上的寿命为2.5ms左右.     

XPS investigation of LPE garnet films

XPS spectra of YIG, YIG:Bi, YIG:Ca and YIG:Co(Ge, Ca) epitaxial garnet films were measured at room temperature. The positions of the main iron, yttrium, oxygen, bismuth, cobalt and lead spectral lines were determined and their changes with the surface treatments were investigated. It was found that divalent and trivalent states of iron and cobalt ions can be resolved, the chemical shifts being in oposite directions.The authors would like to thank Dr. J. imová for careful EPMA analysis of the samples.     

Local field anisotropy in Langmuir-Blodgett films of cadmium arachidate

Lorentz tensor and local field tensor components for uniaxial Langmuir-Blodgett films of cadmium arachidate from 3 to 100 nm thick on silver, polymethyl methacrylate, and glass substrates have been experimentally determined using the data on the film refractive index dispersion in the visible range. The constraints from below on the mean value and anisotropy of the molecular polarizability caused by the intermolecular interactions in the film have been established.     

Polar properties of Langmuir-Blodgett films of copper phthalocyanines

Langmuir-Blodgett films of amphiphilic copper phthalocyanines are obtained. The Stark effect spectra and the spectra of pyro-and photosensitivity of these films are investigated. The following molecular parameters are determined: changes in the polarizability and the dipole moment for individual absorption bands in the Langmuir-Blodgett films and in an isotropic polymer solution. It is shown that the films obtained have photosensitivity due to the charge transfer in the spectral range 600–900 nm. The pyroelectric effect was observed, which indicates that the films have a polar structure.