Anomalous behavior in temporal evolution of ripple wavelength under medium energy Ar+-ion bombardment on Si: A case of initial wavelength selection

We have studied the early stage dynamics of ripple patterns on Si surfaces, in the fluence range of 1-3 x 10(18) ions cm(-2), as induced by medium energy Ar+-ion irradiation at room temperature. Under our experimental conditions, the ripple evolution is found to be in the linear regime, while a clear decreasing trend in the ripple wavelength is observed up to a certain time (fluence). Numerical simulations of a continuum model of ion-sputtered surfaces suggest that this anomalous behavior is due to the relaxation of the surface features of the experimental pristine surface during the initial stage of pattern formation. The observation of this hitherto unobserved behavior of the ripple wavelength seems to have been enabled by the use of medium energy ions, where the ripple wavelengths are found to be order(s) of magnitude larger than those at lower ion energies.The authors are thankful to D. P. Datta from National Institute of Science Education and Research (NISER), Bhubaneswar, for his support and discussion at various stages of this work. R.C. acknowledges funding by MINECO (Spain) through Grant Nos. FIS2012-38866-C05-01 and FIS2015-66020-C2-1-P. S.K.G. acknowledges local support by Universidad Carlos III de Madrid during a short-term visit

Nanofabrication by ion-beam sputtering: fundamentals and applications

Considerable attention has been paid to ion beam sputtering as an effective way to fabricate self-organized nano-patterns on various substrates. The significance of this method for patterning surfaces is that the technique is fast, simple, and less expensive. The possibility to create patterns on very large areas at once makes it even more attractive. This book reviews various fascinating results, understand the underlying physics of ion induced pattern formation, to highlight the potential applications of the patterned surfaces, and to explore the patterning behavior by different irradiatio

Hydrogen depletion from KH<SUB>2</SUB>PO<SUB>4</SUB> under He<SUP>+</SUP> ion bombardment

In view of the ever-growing importance of ion beams in optical material processing, this letter reports room-temperature MeV He<SUP>+</SUP> ion irradiation induced depletion of hydrogen from single crystalline potassium dihydrogen phosphate (KH<SUB>2</SUB>PO<SUB>4</SUB> or KDP) which has wide applications as a nonlinear optical material in optoelectronics technology. Irradiations have been performed using 1.5 MeV He<SUP>+</SUP> ions up to a maximum dose of 2.4 &#215; 10<SUP>15</SUP> ions/cm<SUP>2</SUP>. Simultaneously, hydrogen profiling has been done by detecting the elastically recoiled H atoms. Bare KDP crystals show a hydrogen loss of 72% at the maximum dose whereas Au coated samples show that 60 &#197; of Au layer acts as a barrier to considerably reduce hydrogen depletion from KDP. A possible explanation of these phenomena is suggested

Making Graphene-type Material via Polymerization of Porphyrin

The synthesis of new graphene-type materials (via polymerization of porphyrin macrocycles) through a simple chemical synthetic pathway (at RT) has been demonstrated. This newly synthesized material can be dispersed in water with an average sheet size of few microns and with single layer thickness. As the porphyrin contains four inner ring nitrogen atoms thus the presented polymeric material will be close analogous of N-doped graphene. Porphyrin as the key component to synthesize layered graphene type continuous 2D structure has never been attempted before. </p

Role of Cu‐doping in <scp>CdTe</scp> thin films: Experiments and simulations

Due to its outstanding physical properties, CdTe is used to fabricate high efficiency solar cells. However, its high work function poses a challenge, and hence, to fabricate an efficient CdTe-based solar cell, Cu-doping may be useful. Here, we present the role of temperature-dependent Cu-doping in radio frequency sputter-deposited CdTe films and the related changes occurring in their optical, electrical, structural and microstructural properties. For instance, Cu-doping at different temperatures leads to an increase in the grain size and a reduction in the optical reflectance with increasing temperature. In addition, Kelvin probe force microscopy measurements reveal that the work function is found to be smaller corresponding to the annealing temperature of 473 K, whereas resistivity measurements show that it decreases with increasing temperature (the lowest value of resistivity is found to be 1.8 Â 10 À2 Ωcm). To understand the electronic structure of CdTe before and after Cu-doping, we have carried out first-principles density functional theory (DFT) simulation, which reveals a strong hybridization among Cu, Cd and Te atoms. This study paves the way to fabricate efficient Cu-doped CdTe-based solar cells

Controllable physicochemical properties of WOx thin films grown under glancing angle

In this work, various physicochemical properties are investigated in nanostructured WOx thin films prepared by radio-frequency magnetron sputtering for optoelectronic applications. A glancing angle of 87° is employed to grow films of different thicknesses, which are then exposed to post-growth annealing. Detailed local probe analyses in terms of morphology and work function of WOx films are carried out to investigate thickness-dependent property modulations of the as-deposited and annealed films. The analyses show a reasonably good correlation with photoelectron spectroscopic measurements on the films and the bulk I–V characteristics acquired on a series of WOx/p-Si heterojunction diodes. The presence of a critical WOx thickness is identified to regulate the rectification ratio values at the WOx/p-Si heterostructures and increase in series resistance within the bulk of the films. The present study provides valuable insights to correlate optical, electrical, and structural properties of WOx thin films, which will be beneficial for fabricating WOx-based optoelectronic devices, including photovoltaic cells