Co-implantation, with overlapping implantation projected ranges, of Si and of the doping species (P, As, or B), followed by a single thermal anneal step, is proved to be a viable route to form doped Si-nc’s embedded in SiO2, with diameters of a few nanometers. Extensive results of the evolution of the Si-nc’s related photoluminescence, as a function of the dopant implanted dose, are presented and discussed. Atomic Probe Tomography (APT) is used to image directly the spatial distribution of the various species at the atomic scale. The 3D APT data demonstrate that n-type dopant atoms (P and As) are efficiently introduced in the "bulk" of the Sinanocrystals, whereas B atoms are preferentially located at their periphery, at the Si/SiO2 interface.

In this paper we propose a few helium ion microscope (HIM)-based methods for sample preparation and modification. In particular we report the use of the HIM to make thin wedge SrTiO3 samples without significant artifacts, the possibility to reshape thin metal lines on an electron transparent membrane and the new method of HIM sample preparation by in situ heating of the samples during He-beam illumination.

Embedded Si nano-particles of average size around 5nm were synthesized in an amorphous Si matrix by two stage ion implantation processes. It has been observed that amorphous Si (a-Si) layers were recrystallized using 50 MeV Au ions with enhanced regrowth rate with activation energy in the range of 0.29 eV. During the crystallization process Si nanocrystals were formed in the a-Si layers due to sudden quenching of the molten tracks created by MeV Au ions. The recrystalizations were confirmed by Rutherford backscattering spectrometry-Channeling (RBSC) technique. The structural modification and nanocluster creation that emerged during recrystallization process was observed in high-resolution transmission electron microscopy and photoluminescence (PL) spectroscopy. The PL emission was observed over a broad band of 2.8 – 3.4 eV and centered at 3.25 eV. The Si nano-crystal formation can be explain by a mechanism combining the melting within the ion tracks by thermal spike process and the subsequent recrystallization nucleated from the crystalline sides at the interface.

In this work, the first-principles computational scheme of electron-ion dynamics based on the time-dependent density functional theory is presented as a tool to study dynamical phenomena induced by light. Two applications of computations for photo-induced phenomena are shown. The one is structural change induced by intense and short laser shot with a purpose to simulate experiments using the femtosecond laser. The other is photo-excitation and subsequent carrier splitting into electrons and holes, which is a key process needed in photovoltaic materials.

We have employed atomic force and Kelvin-Probe force microscopy to study graphene sheets exfoliated on TiO2 under the influence of local heating achieved by laser irradiation. Exfoliation and irradiation took place under ambient conditions, the measurements were performed in ultra high vacuum. We show that after irradiation times of 6 min, an increase of the surface potential is observed which indicates a decrease of p-type carrier concentration. We attribute this effect to the removal of adsorbates like water and oxygen. After irradiation times of 12 min our topography images reveal severe structural modifications of graphene. These resemble the nanocrystallite network which form on graphene/SiO2 but after much longer irradiation times. From our results we propose that short laser heating at moderate powers might offer a way to clean graphene without inducing unwanted structural modifications.

We describe a scalable synthesis process for the production and patterning of polymer matrix nanocomposites (PMNCs) using femtosecond laser irradiation to target specific functional behaviors. A modified, in situ chemical vapor deposition (CVD), nanoinfusion process was used to nucleate and grow nanoparticles in the bulk of an optically transparent polytetrafluoroethylene-co-hexafluoropropylene (FEP) polymer matrix. Metallic nanoparticles synthesized with this process can have a strong optical absorption at their surface plasmon resonance (SPR) frequency and we have utilized this property to selectively irradiate and pattern nanocomposites via femtosecond, photothermal heating. If the nanoparticle environment includes species used for chemical vapor deposition, the heat causes a localized decomposition of the precursor species in the immediate vicinity of the nanoparticle leading to a variety of core-shell nanostructures. Using this processing scheme, we have grown shells of tungsten oxide around silver nanoparticles within the polymer matrix resulting in a 40 nm red shift in the SPR of the silver nanoparticles in regions of the material exposed to femtosecond laser pulses. This process has also been adapted to polymers containing tungsten oxide nanoparticles so that the photocatalytic behavior of the particles could be used to the decompose precursor species in the immediate vicinity of the irradiated nanoparticles. These results demonstrate that, by using optical masks and laser processing, it is possible to synthesize nanocomposites with a high degree of control over the location, composition, size, and distribution of nanoparticles within a polymer matrix resulting in patterned materials with tailored electrical, optical, and photocatalytic properties.

We carried out laser ablation of three organic molecules, rubrene (Rb), Oralith Brilliant Pink R (BP) and quinacridonequinone (QQ) in a poor solvent, water. As a result, nanoparticles of BP and QQ were formed, but those of Rb were not formed because of photodissociation. For a rigid molecule, QQ, optical properties of colloidal solutions were investigated in relation to the size of the included nanoparticles. A linear correlation between the blue shift of the absorption peak energy and the decrease in the diameter of the nanoparticles was found, indicating that the nanoparticle diameter can be easily estimated from the absorption spectrum of a colloidal solution. From the solution, a nanoparticle film was fabricated on an electrode by the electrophoretic deposition method.

This experimental study presents a comparison of differently tensile stressed silicon nitride (SiN) layers and their response to irradiation in a vacuum ultraviolet (VUV) curing system. Therefore, three types of silicon nitride with initial stress levels of 450 MPa, 700 MPa and 980 MPa were deposited by plasma enhanced chemical vapor deposition (PECVD). In contrast to industrial standard VUV curing with broadband lamps ≥ 220 nm radiation wavelengths, we analyzed the effects of curing with single wavelengths at 172 nm and 222 nm. The samples were characterized by Fourier Transform Infrared Spectroscopy, ellipsometry, and wafer bow measurement. It could be shown that high energy photons are able to dehydrogenize SiN films more than lower energetic photons compared with lower Si-N-Si crosslinking effects. Furthermore, we could show that a dual combined 172 nm and 222 nm VUV curing procedure can produce films with very low hydrogen concentration and high percentage of structural units consisting of Si-N-Si bonds. In conclusion of this study, an up to +900 MPa stress increasing process could be established.

Ge quantum dots were grown on Si(100)-(2x1) using pulsed laser deposition while the laser is also exciting the substrate during film growth. The growth mode and morphology was probed by scanning tunneling microscopy (STM). Epitaxial growth at a substrate temperature of ∼250 °C was achieved by using laser excitation of the substrate. The morphology of the quantum dots changed with increased laser excitation energy density although the faceting of the individual quantum dots remained the same. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed.