Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 ◦C and the effects of thermal annealing in air between 200 and 400 ◦C for between 1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of 1.7×10−3 Torr by DC power sputtering (100W) at substrate temperatures between 40 and 400 ◦C exhibited resistivities in the range 3.0–5.7×10−5 Ωm and transmissions in the range 71%–79%. After deposition and annealing in air at 300◦C for 1 h, the films showed resistivities in the range 2.9–4.0×10−5 Ωm and transmissions in the range 78%–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 ◦C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 ◦C, and up to 400 ◦C, had domains with crystalline structures. After deposition and annealing in air at 300 ◦C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 ◦C to 300 ◦C, and annealing in air at 300◦C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 ◦C and annealing in air at 300◦C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated.

The conformational transitions (helix-coil transitions) of three hairpin triple helices, models 5’.(A-G), + 5’-(T-C),-T,- (hrC-T), [CY]. S-&G), + 5’-(T-h’C),-T,-(C-T), [YC] and 5’.(A-G), + 5’-(T-h’C),-T,-(h’C-T), [YY], are characterized in this work by UV spectroscopy. Melting of these triplexes is biphasic. and the profiles are used to obtain the thermodynamic parameters. The thermodynamic properties of the hairpin triplex are Tm= 19.45°C and Δ Hvh, = 293. I2 kJ molt-’ for CY, Tm= 22.85°C and Δ Hvh, = 256.63 kJ mol- ’ for YC and Tm = 28.47 °Cand ΔHvh, = 234.68 kJ molt ’ for YY at pH 4.4. Those of the duplex are Tm = 30.5O°C and AH,, = 427.09 kJ molt-’ for CY, Tm= 32.96°C and Δ Hvh, = 374.47 kJ molt ’ for YC and Tm = 33.24°C and Δ Hvh, = 329.67 kJ mol- ’ for YY at pH 4.4. The distinct transitions of triplex to duplex and duplex to single strands are analyzed win g the nearest-neighbor Ising model. Electrostatic effects on each conformation are also analyzed. 0 1997 Elsevier Science B.V.

Three triple-helical hairpin DNAs with substitution of 5-bromocytosine for cytosine in different strands have been investigated by molecular mechanics and Raman spectroscopy. The stability of the three substituted triplexes were compared with the corresponding unsubstituted triplex DNA by the molecular mechanics method. Base stacking interactions and strand]strand interactions of each triplex were analyzed in detail. Sugar conformations in these triplexes have been determined by both vibrational spectroscopy and molecular dynamics simulation. The hairpin triplexes with substitution occurring in strand I or both in strands I and III have the main sugar conformation of C39-endo, while the triplex with substitution occurring in strand III is the combination of C39-endo and C29-endo sugar conformation. Theoretical results are basically in agreement with experiments. Q 1999 Elsevier Science B.V. All rights reserved.

Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) ere performed on monolayer film of NiTPP supported on Au(111) under ultrahigh vacuum (UHV) conditions. The constant current STM images show remarkable bias dependence. High resolution STM data clearly show the individual NiTPP molecules and allow easy differentiation between NiTPP and CoTPP reported before. Scanning tunneling spectra, as a function of molecule-tip separation, were acquired over a range of tip motion of 0.42 nm. Spectra do not show the variation in band splitting with tip distance. It appears for molecules such as NiTPP that the average potential at the molecule is essentially the same at the same metal substrate. For molecules of the height of NiTPP, the scanning tunneling spectra should give reliable occupied and unoccupied orbital energies over a wide range of tipmolecule distances.

We describe in this paper the fabrication of two-and one-dimensional nano-structures with organic molecular beam epitaxy (OMBE) principle based on controlled self-assembly by using adsorbate-ubstrate and intermolecular interactions that are important in molecular fabrication. Cu(100) single crystal was used as substrate in fabricating molecular nanostructures. Scanning tunneling microscopy (STM) experiments confirmed that Zn-tetra-[3,5-di-t-butylphenyl]porphyrin molecules can be used to fabricate both monolayer and molecular wire on Cu(100) surface simultaneously, and the latter is arranged on the terrace edges. We herein briefly discuss the selectivity in terms of a mechanism in which the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of the molecules interact with the surface.