Measurement of the spatial characteristics of an erosive silicon laser plasma using small-sized high-resolution spectrometers

The spatial characteristics of the erosion laser plasma are investigated. The application of small-sized spectrometers of the visible and ultraviolet ranges for recording the spectrum of plasma radiation is considered. Erosive laser plasma is formed on the surface of a silicon target under the action of pulsed laser radiation with a wavelength of 1064 nm under normal atmospheric conditions. The laser plasma torch was scanned using a movable slit diaphragm oriented parallel to the target surface. The emission of erosion laser plasma was recorded using small-size spectrometers. Based on the obtained plasma emission spectra, the dependences of the intensity of the spectral lines of silicon on the geometric position of the slit diaphragm are revealed. A comparison is made of the intensities of the spectral lines of silicon on the polished and grinded sides of the target.

Tailoring Photoluminescence from Si-Based Nanocrystals Prepared by Pulsed Laser Ablation in He-N2 Gas Mixtures

Using methods of pulsed laser ablation from a silicon target in helium (He)-nitrogen (N2) gas mixtures maintained at reduced pressures (0.5–5 Torr), we fabricated substrate-supported silicon (Si) nanocrystal-based films exhibiting a strong photoluminescence (PL) emission, which depended on the He/N2 ratio. We show that, in the case of ablation in pure He gas, Si nanocrystals exhibit PL bands centered in the “red - near infrared” (maximum at 760 nm) and “green” (centered at 550 nm) spectral regions, which can be attributed to quantum-confined excitonic states in small Si nanocrystals and to local electronic states in amorphous silicon suboxide (a-SiOx) coating, respectively, while the addition of N2 leads to the generation of an intense “green-yellow” PL band centered at 580 nm. The origin of the latter band is attributed to a radiative recombination in amorphous oxynitride (a-SiNxOy) coating of Si nanocrystals. PL transients of Si nanocrystals with SiOx and a-SiNxOy coatings demonstrate nonexponential decays in the micro- and submicrosecond time scales with rates depending on nitrogen content in the mixture. After milling by ultrasound and dispersing in water, Si nanocrystals can be used as efficient non-toxic markers for bioimaging, while the observed spectral tailoring effect makes possible an adjustment of the PL emission of such markers to a concrete bioimaging task.

Damage Formation and Calculation of Energy Loss during Implantation of Antimony and Boron Ion in Silicon Target

The aim of this research work is a computational study of damage profile and visualization of the ion implantation graph obtained from the simulation method using SRIM-2013 software. SRIM (Stopping and Range of Ions in Matter) helps in calculating the energy required for an ion to obtain maximum concentration for desirable range and TRIM (Transport of Ions in Matter) is used to calculate doping statistics and calculation of energy loss. The main objective of this work is to get knowledge about the graphical study of ion range, distribution, stopping power and energy loss during implantation of antimony and boron ion on the silicon target within 0 to 3500 Å target depth. The implantations of 10,000 antimony and boron ions are accelerated by 350 keV and 45 keV energy in silicon monolayer target to obtain maximum defects concentration. The result of the ionization process indicates that 11.68% of the total energy of antimony ion and 65.25% of the total energy of boron ion are lost during the ionization process. This indicates that lighter boron ion causes more ionization than the heavier antimony ion for the same projected range.

Shock-induced Amorphization in Covalently Bonded Solids

Deposition of powerful pulsed laser energy onto a material, ablates its surface and drives a compressive shock wave propagating through it. Using this technique, unprecedented states of matter with extremely high pressures, temperatures, and strain rates can be experimentally studied. Here we report on laser-shock induced amorphization in four covalently bonded solids, namely silicon (Si), germanium (Ge), boron carbide (B4C) and silicon carbide (SiC). Post shock transmission electron microscopy reveals that the newly formed amorphous materials exhibit a shear band alike morphology, suggesting that shear stress play a dominant role in this process. The density of these amorphous band decreases as a function of the distance to the surface and eventually disappeared at certain depth, which is coincident with the decay of the shock wave and indicates that there might be a critical stress for the onset of amorphization. Synchrotron XRay tomography of a recovered silicon target shows that large amounts of cracks are formed within the materials and the density also decrease with depth. Unlike amorphous bands, these cracks can propagate through the target, albeit without shattering the entire material. It is proposed that shock-induced amorphization is a new deformation mechanism of matter under extremely high rate deformation.

Emission enhancement of laser-induced breakdown spectroscopy by increasing sample temperature combined with spatial confinement

Spatial confinement and increasing sample temperature were used simultaneously to improve plasma emission from a silicon target in air.