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PACS. 4 2 . W -Optical transient phenomena, self-induced transparency, optical saturation and related effects (inc. photon echoes, free induction decay and optical mutation). PACS. 82.503 -Photodissociation, photoionization a8 studied by luminescence and radiationless transitions. PACS. 42.30N -Optical storage and retrieval.

Optical properties of aged WS2 monolayers grown by CVD method on Si/SiO2 substrates are studied using temperature dependent photoluminescence and reflectance contrast spectroscopy. Aged WS2 monolayers have a typical surface roughness about 0.5 nm and, in addition, a high density of nanoparticles (nanocaps) with the base diameter about 30 nm and average height of 7 nm. The A-exciton of aged monolayer has a peak position at 1.951 eV while in as-grown monolayer the peak is at about 24 meV higher energy at room temperature. This red-shift is explained using local tensile strain concept, where strain value of 2.1% was calculated for these nanocap regions. Strained nanocaps have lower band gap energy and excitons will funnel into these regions. At T=10K a double exciton and trion peaks were revealed. The separation between double peaks is about 20 meV and the origin of higher energy peaks is related to the optical band gap energy fluctuations caused by random distribution of local tensile strain due to increased surface roughness. In addition, a wide defect related exciton band XD was found at about 1.93 eV in all aged monolayers. It is shown that the theory of localized excitons describes well the temperature dependence of peak position and halfwidth of the A-exciton band. The possible origin of nanocaps is also discussed.

Abstract:The Raman spectroscopy method was used for structural characterization of TiO 2 thin films prepared by atomic layer deposition (ALD) and pulsed laser deposition (PLD) on fused silica and single-crystal silicon and sapphire substrates. Using ALD, anatase thin films were grown on silica and silicon substrates at temperatures 125-425 • C. At higher deposition temperatures, mixed anatase and rutile phases grew on these substrates. Post-growth annealing resulted in anatase-to-rutile phase transitions at 750 • C in the case of pure anatase films. The films that contained chlorine residues and were amorphous in their as-grown stage transformed into anatase phase at 400 • C and retained this phase even after annealing at 900 • C. On single crystal sapphire substrates, phase-pure rutile films were obtained by ALD at 425 • C and higher temperatures without additional annealing. Thin films that predominantly contained brookite phase were grown by PLD on silica substrates using rutile as a starting material.

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We have developed a model to describe the inhomogeneous broadening of optical spectra in the substitutionally disordered crystals. The comparison with the experimental f -f fluorescence spectra of SrFClxBrl_x:Sm2+ (O~x~ I) allowed to establish, in a very detailed manner, the relationship between the inhomogeneous spectral distribution and the crystal structure around the Sm 2 + impurity. to 128.95.64.60. Redistribution subject to AIP license or copyright; see http://jcp.aip.org/about/rights_and_permissions x -value 1 O.5~--O~=====14*500~=====1~M~5~O~-Emission Frequency [cm-I ] FIG. 2. Fluorescence spectra of SrFClxBrl_x:Sm2+ 5 Do -7 F 0 transition; T=lOO K.

This paper further discusses a concept of creating a self-sensing ionic polymer-metal composite (IPMC) actuating device with patterned surface electrodes where the actuator and sensor elements are separated by a grounded shielding electrode. Different patterning methods are discussed and compared in detail; the presented experimental data give an understanding of the qualitative properties of the patterns created. Finally, an electromechanical model of the device is proposed and validated.

Graphene as a single-atomic-layer material is fully exposed to environmental factors and has therefore a great potential for the creation of sensitive gas sensors. However, in order to realize this potential for different polluting gases, graphene has to be functionalized -adsorption centers of different types and with high affinity to target gases have to be created at its surface. In the present work, the modification of graphene by small amounts of laser-ablated materials is introduced for this purpose as a versatile and precise tool. The approach has been demonstrated with two very different materials chosen for pulsed laser deposition (PLD) -a metal (Ag) and a dielectric oxide (ZrO2). It was shown that the gas response and its recovery rate can be significantly enhanced by choosing the PLD target material and deposition conditions. The response to NO2 gas in air was amplified up to 40 times in the case of PLD-modified graphene, in comparison with pristine graphene, and it reached 7-8% at 40 ppb of NO2 and 20-30% at 1 ppm of NO2. The PLD process was conducted in a background gas (5 x10 -2 mbar oxygen or nitrogen) and resulted in the atomic areal