UV Laser Photodeposition of Nanotextured Poly(hydridomethylsiloxane) Powder from Gaseous 1,3-Dimethyldisiloxane

Abstract

Research into nanomaterials is growing rapidly due to the unique properties of these materials and their potential in applied science. Various silicon-based nanostructured materials, such as SiO x nanowires, [1,2] SiC and Si 3 N 4 nanorods, [3,4] nanosize Si/O/C composites, [5] and SiO x nanoflowers [6] have been prepared and are potentially useful as optical devices, semiconductors, catalyst supports, and precursors of novel bulk materials. Almost 20 years ago, sinterable powders composed of Si, SiC, and Si 3 N 4 nanosize particles were produced by infrared (IR) laser heating of silane, either on its own, or mixed with ammonia or hydrocarbons. [7] Later, nanostructured films of Si/C/H [8±10] and Si/C/F [11,12] phases were produced by infrared or ultraviolet (UV) laser photolysis of single organosilicon precursors.We have described how unique woven textures of Si/C/ O/F nanochains were obtained via IR laser±induced chemistry in gaseous mixtures of silane and hexafluoroacetone, [13] and recently shown that the nanostructured chains creating a woven network in polyhydridosiloxane films were produced by UV laser photolysis [14] and IR laser thermolysis [15] of gaseous disiloxane H 3 SiOSiH 3 .In this paper we give another example of laser CVD silicon-based nanostructures, and report on the preparation of a fluffy nanotextured powder of poly(hydridomethylsiloxane) achieved through high-fluence UV laser irradiation of gaseous 1,3-dimethyldisiloxane (DMDSO).The UV absorption spectrum of DMDSO (Fig. 1) shows two maxima at 197 nm and 200 nm, and absorptivities at 193 nm, 197 nm, and 200 nm of 2 10 ±3 torr ±1 cm ±1 , 2.1 10 ±3 torr ±1 cm ±1 , and 1.6 10 ±3 torr ±1 cm ±1 , respectively. High-fluence ArF laser irradiation (193 nm) of DMDSO results in a bright luminescence observed in the laser beam area behind the entrance window of the reactor; in the formation of hydrogen, volatile hydrocarbons, and methylsilanes; and in the CVD of white flakes of a solid material that cover the inside of the reactor. The photolytic progress is reasonably fast (Fig. 2), but is impeded by the development of a thin film of the white solid (opaque to 193 nm radiation, Fig. 1) on the entrance window of the reactor. The photolysis is therefore best conducted by periodically passing the laser beam through different areas of the entrance window. Fig. 1. Absorption UV spectra of a) DMDSO and b) the deposit.Fig. 2. Progress of DMDSO photolysis as function of the number of pulses (irradiation conditions are given in the Experimental section).

IR Laser‐Induced Carbothermal Reduction of Silica

“…Nanosized silicon oxycarbide or silicon oxide–carbon composites have not been particularly examined so far, although nanosized H‐containing Si/C/O/ (polyoxocarbosilane) phases, similar to silicon oxycarbide, were prepared by chemical vapor deposition using UV laser photolysis30–32 and IR laser thermolysis33–35 of disiloxanes, or by UVlaser‐induced conversion of silica 36…”

UV Laser Photolysis of Disiloxanes for Chemical Vapor Deposition of Nano-Textured Silicones

“…It is known , that the UV photolysis of Si−O bond-containing saturated organosilanes at wavelengths below 200 nm is controlled by cleavage of weak C−Si bonds. We have briefly reported on UV laser-induced photolysis of disiloxane (H 3 SiOSiH 3 ) and 1,3-dimethyldisiloxane (CH 3 H 2 SiOSiH 2 CH 3 ).…”