Thin polycrystalline

EDSA of thin polycrystalline films has several advantages First of all the availability of a wide beam (100-400 pm in diameter) which irradiates a large area with a large amount of micro-crystals of different orientations [1, 2]. This results into a special t5q)e of diffraction patterns (DP) (see Fig.l). Thus it is possible to extract from a single DP a full 3D data set of structure amplitudes. That allows one to perform a detailed structure analysis with good resolution for determining structure parameters, reconstruction of ESP and electron density. 

Diffraction patterns from thin polycrystalline Ge films were measured by the eleetron diffraetometer. After refinement of scale and thermal factors and corrections for the primary extinetion within the two-beam approximation, the parameters k (spherieal deeompression of valence eleetron shell) and multipoles P32- and P40 (anisotropy of electron density) were ealeulated (Table 4). The residual faetor R ealeulated from the experimental and theoretical amplitudes (the latter were ealeulated by the LAPW method, Lu Z.W., et al. Phys.Rev. 1993, B47, 9385) is 2.07% and proofs the high quality of the experimental. 

The most exciting property of these materials is that thin polycrystalline films can behave as two dimensional Josephson Tunnel Junction Arrays (110) displaying remarkably good electromagnetic coupling (111) both as emitters and receivers. Alternating current to direct current conversion has been observed in bulk samples (112), but the thin film geometry allows use of one film as a radiation emitter, and another film as the receiver (111). 

Figure 9.12 Transport of diffusant through a thin polycrystalline film by grain-boundary diffusion.

Recombination of electrons and holes at grain boundaries in thin, polycrystalline films of semiconductors is a key problem that requires solution if efficient and inexpensive solar cells are to be developed. This problem is quite similar to the extensively studied phenomenon of recombination at semiconductor surfaces. Both involve the electronic states associated with the abrupt discontinuity in the chemical bonding at an interface. 

IR transmission spectra (T) of the thin polycrystalline specimens or powders were measured using IR microscope of the Fourier-spectrometer at room temperature in the spectral range of 600 5,000 cm-1. Optical absorption spectra were calculated as -ln(T). Figure 11.11 demonstrates normalized absorption spectra of fulleranes C60Hx with x = 36, 42, 48 and 60 together with the well known spectrum of fullerit... 

Notwithstanding the capability for measurement of photoemission spectra at pressures up to 1 mbar, the original construction of the gas cell was not suitable for carrying out experiments under catalytic reaction conditions. To provide the short distance between the sample surface and aperture for the exit of electrons (or a short path of the photoelectrons in the zone at the higher pressure), the equipment supplier decreased the dimensions of the gas cell. A section of the cell, together with the standard sample holder and a typical sample, is shown in Figure 4A this design limits the size of the sample so that only thin polycrystalline foils can be... 

MALDI-MS was performed using a Kratos Kompact MALDI III mass spectrometer fitted with a standard 337 nm nitrogen laser, and operated in the linear mode at an accelerating voltage of 20 kV. Two sample preparation methods were used (1) for collected peptides, 0.3 pL aliquots of sample and matrix (a-cyano-4-hydroxy cinnamic acid, Biomolecular Separations, Inc.) were mixed on the probe slide and allowed to air dry or (2) for unfiactionated digests, a thin polycrystalline film was prepared according to (11) (with modifications for use on a probe slide (12)), matrix and sample aliquots were mixed (usually 0.3 pL each) on this surface and prior to drying, rinsed twice with 2 pL of deionized water. 

With regard to the crystallized compounds, a distinction must be made on the one hand between the quantitative results in polarized light, which are limited toward the ultraviolet because of the very intense absorbance of the crystals, and on the other hand semi-quantitative results obtained in the ultraviolet with natural light from thin polycrystalline films evaporated on a quartz plate. 

The intensification of the band identified by Moncuit aig a u for the free ion (situated at 2,800 A for the platinocyanides and at 2,400 A for the palladocyanides) when working on thin polycrystalline sheets can easily be explained by the preferential orientation of the crystals on the quartz plate. It must be remembered that this band related to incident vibrations polarized perpendicular to planar groups no longer appears clearly at this energy for the complexes with alkali-metal and alkaline-earth cations. 

Presently there exists a strong research interest in the understanding, development, and optimisation of organic field effect transistors (OFETs) [1, 2]. Two classes of semiconducting organic materials are considered, namely molecular materials which are processed into thin films by vacuum sublimation [1, 2], and polymers which are deposited onto substrates in the form of solutions, for instance by spin coating [3]. In this chapter we report on OFETs based on thin polycrystalline films of the molecular material pentacene (Pc) as the semiconducting material. 

Both transitions are lowered in energy, but the Rydberg states are much more affected. Figure 3 gives the vertical excitation for the pertinent processes. As far as the absorption spectrum of tetramethylethylene is concerned, it shows a strong V N absorption band with its maximum centered at 185 run. Another band, well separated from the previous one, is located between 210 and 240 nm (48000 - 42000 cm ). In a thin polycrystalline film (T = 23 K), this band is... 

Doping densities in single-crystal semiconductor samples can usually be determined from capacitance and voltage measurements uing suitable electrolyte contacts. However, in the case thin polycrystalline layers fabricated for PV devices, dark currents arising from cracks and pinholes often make interpretation of impedance data difficult In this case a different approach based on analysis of the EQE response may be useful. If the minority diffusion length in the sample is sufficiently small to fulfill the condition aL 1-as is usually the case for... 

One final procedure for minimizing substrate Raman scattering interference in thin polycrystalline films deposited on silica is based upon the polarization properties of the scattered light (16). Inherent molecular disorder present in vitreous silica substrates results in marked polarization anisotropy of the Raman-scattered light from the substrate. Raman scattering from a deposited polycrystalline film is isotropic since the individual randomly-oriented grains act to scramble the... 

The optical properti es of thin polycrystalline films are influenced by the extent of grain orientation, which is also manifested in the Raman band intensities for vibrational modes of different symmetry. Figure 9a illustrates the two strongest Raman active modes for the rutile phase of Ti02. The Eg assigned mode exhibits a vibrational frequency of 444 cm"l, while the frequency for the Aig mode is 608 cm l. A series of 0.6 micrometer thick rutile films with variable ordering in the grain structure was prepared by sputter deposition techniques. Refracti ve indices... 

The ex situ studies of xanthate adsorption under chemically controlled conditions have been conducted by transmission [487-489] and DRIFTS [375-377, 385, 386, 480, 484, 490-495] on powdered sulfides, by ATR on thin polycrystalline synthetic films of PbS [496-498] and single-crystal sphalerite [499], and by IRRAS on sulfide and metal plates [327, 329, 330, 481, 482, 500],... 

Pertsev, N.A., Zembilgotov, A.G., and Waser, R. 1998. Effective dielectric and piezoelectric constants of thin polycrystalline ferroelectric films. Physics of the Solid State 40 [12] 2002-2008. 

SAMs of alkanethiolates that present a wide range of functional groups on thin polycrystalline films of gold and silver are easy to prepare, and have been broadly applied in various fundamental and technological studies. They are well-ordered, and the best characterized systems of organic monolayers presently known. In this chapter, we focus on them. 

For the case of a polycrystalline material the analysis is a little more complex because the grain-boundary energy enters into the balance. Typically when a thin, polycrystalline wire is annealed at high temperature the grain boundaries will rotate until they are normal to the wire axis see Figure 4.20(b). In this case the energy balance will be... 

X in PDAs and are of continuing interest. However, poly-PTS crystals grown to date do not have optically flat surfaces, and their study has been facilitated by immersion in diiomethane, which has a refractive index comparable to the polymer in the near infrared region (13). Thin polycrystalline films of poly-PTS (16) do not improve the situation in that they have significant transmission losses in the near infrared (17). 

The role of grain boundary diffusion in stress relaxation in a thin polycrystalline film on a substrate is considered here, as a vehicle for illustrating the... 

Choi, Y. and Suresh, S. (2002), Size effects on the mechanical properties of thin polycrystalline films on substrates, Acta Materialia 50, 1881-1883. 

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