The effect of KrF excimer laser energy density (below and above the ablation threshold), number of shots and angle of laser incidence on the morphological reconstruction, structure and specular reflectance of Si[311] surfaces is reported. At low energy densities (0.1 to 0.3 J/cm2) laser irradiation results in a variety of nanostructures, depending on laser energy density and number of shots, such as nanopores (40-60 nm dia) and nanoparticles (40-80 nm dia). At energies greater than the laser ablation threshold (2 to 5 J/cm2) the formation of nanowires (200 nm dia, 6-8 microm length), and closely spaced silicon nanograins (100-150 nm dia) is observed. Experiments to study the effect of laser irradiation in the proximity of a fixed shape such as a linear step edge in the form of a stainless steel blade and a cylindrical cross-section Cu wire were also carried out. In both cases, linearly organized nanoparticles (150-200 nm diameter) and nanowires (60-80 nm diameter) formed close to the edge. There is a systematic degradation of long-range order with the number of shots and laser energy density as evidenced from X-ray diffraction studies. At an energy density of 2 J/cm2, and 100 shots the [311] oriented silicon surface made a transition to a randomly oriented nanocrystalline state.

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Cu x O-based resistive random access memory (RRAM) devices are fabricated with low, medium, and high oxygen affinity metals as the top electrode and gold and platinum as the bottom electrode. Switching performance of the device with varying oxygen affinity is observed. The variation, mean, and the cycle percentage of V set and V reset values decrease with the decrease in oxygen affinity but increase in the case of I reset . The reset power parameter decreases with oxygen affinity of metal electrodes (OAME). A generalized figure of merit (FM), which considers all the parameters (variation, mean, and cycles count) of a switching parameter (V set , V reset , I reset , and P reset ), is introduced to explain the performance. The FM also confirms the variation in switching parameters with oxygen affinity. This reveals that the performance of the device is improved with the decrease in oxygen affinity. The device fabricated with low oxygen affinity metal electrode, Ni, shows the best performance among all the Cu x O-based RRAM devices. Further improvement in device performance is achieved by changing the bottom electrode from Au to Pt with the top electrode being retained as a low oxygen affinity metal. This combination is shown to be the best in terms of retention and endurance.

The deposition and annealing of nickel-amorphous silicon (a-Si) bilayer thin films on fused silica substrates is reported. Two bilayer geometries that consisted of an a-Si layer and the Ni layer over and below it, respectively, are investigated. The bilayers were deposited at temperatures between 200 and 550 °C, and in each case, postdeposition annealed in vacuum at the temperature of deposition to study the effect of geometry on the diffusion process. The diffusion process is illustrated using cross-sectional scanning electron microscopy in conjunction with energy dispersive spectrometry. The study reveals that, independent of geometry, the top surface of Ni/Si bilayers is abundant in Ni after annealing. In the geometry when Ni is at the top, x-ray diffraction and Raman spectroscopy studies reveal that, at temperatures <400 °C, there is no reaction between the Ni and the Si. The Ni-Si reaction occurs at temperatures >400 °C to form NiSi2. However, when Ni is at the bottom of the Si layer at a temperature of 200 °C itself, a nickel rich silicide Ni31Si12 forms. This is in addition to nanocrystallization of Ni. In the case when Nickel is at the bottom, most of the energy is taken up in diffusion and crystallization of Ni. The remaining energy is then used to react with the Si, leading to the formation of Ni31Si12 and its crystallization. At temperatures >500 °C, Ni reacts with Si to form NiSi2. When Ni is at the top, since it is already at its preferred location most of the energy is used up in crystallization of Ni and reaction of Ni with Si and crystallization of NiSi2. Importantly, in both cases, the energy is insufficient to cause crystallization of Si.

Ag films of 5 nm thickness were iodized for durations up to 3 h leading to the formation of b-AgI structure. The water contact angle (WCA) for the uniodized and as-deposited Ag film was 107.2 which is decreased to 70.7 on iodization for 3 h. In contrast, the Ag films annealed at 300 C for 2 h prior to iodization showed a water contact angle of 40.3 . The WCA decreased further to 14.9 after iodization for 3 h. This hydrophobic-hydrophilic transition can be related to the chemical modification of the surface change in crystal structure and variation in surface roughness. Significantly, the films also exhibited reversible wettabilty under UV irradiation.

A simple and facile solution phase synthesis of large-scale, microto-nanometer sized bismuth triiodide (BiI 3 ) single crystalline hexagonal plates is reported. It is demonstrated that under optimized conditions the reactions result in dominant exposed (001) facets. Because of the large size, high surface-tovolume ratio, and thickness, BiI 3 nanoplatelets are attractive as visible light photodetectors. At 1 V bias, the photoresponsivity is 0.87 A W −1 ; the specific detectivity is 4.8 × 10 12 jones with a response rise time of 1 s and a fall time of 0.97 s. The Kelvin probe force microscope images revealed that the surface potential difference across the junction was 42.5 mV, which is attributed to the work function difference between the sample and substrate. The results of this study indicate that single hexagonal platelets of BiI 3 are very promising for visible light photodetector applications.