Rapid laser sintering of metal nano-particles inks.

Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 µs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

Enhanced photochemistry of ethyl chloride on Ag nanoparticles.

Enhanced photodecomposition of ethyl chloride (EC) adsorbed on SiO2/Si (100) supported silver nanoparticles (Ag NPs) under ultrahigh vacuum (UHV) conditions has been studied in order to assess the potential contribution of plasmonic effects. The cross section for photodecomposition of EC and overall photoyield were found to increase with increasing photon energy regardless of the plasmon resonant wavelength and with Ag coverage without any noticeable particle size effect. The influence of EC-Ag NPs separation distance on the rate of EC decomposition was studied in order to examine potential local electric field influence on the photodissociation process. Long (∼5 nm) photoactivity decay distance has been observed which excludes local surface plasmon dominance in the photodecomposition event. These findings suggest that the alignment of excited electron energy and adsorbate affinity levels is central for efficient photochemical reactions, whereas short-range electric field enhancement by plasmon excitation on top and at the immediate vicinity of silver nanoparticles does not have any measurable effect.

Tailor-made oxide architectures attained by molecularly permeable metal-oxide organic hybrid thin films.

Tailor-made metal oxide (MO) thin films with controlled compositions, electronic structures, and architectures are obtained via molecular layer deposition (MLD) and solution treatment. Step-wise formation of permeable hybrid films by MLD followed by chemical modification in solution benefits from the versatility of gas phase reactivity on surfaces while maintaining flexibility which is more common at the liquid phase.

Highly efficient photoinduced desorption of N2O and CO from porous silicon.

Photoinduced desorption (PID) of N(2)O and CO from porous silicon (PSi) samples is reported. Both adsorbates exhibit unusually large cross sections for PID at 193 nm, up to 10(-15) cm(2), 2-3 orders of magnitude larger than the literature values for similar processes on flat Si. Under this UV irradiation, N(2)O molecules undergo photodissociation (a competing process leading to surface oxidation) with a cross section that is 2 orders of magnitude smaller than photodesorption. In the case of CO desorption is the exclusive photodepletion mechanism. PID efficiency decreases with increasing CO coverage suggesting PID hindrance by interactions among the desorbing CO molecules leading to re-adsorption at higher coverage. The wavelength and fluence dependence measurements exclude the possibility of laser induced thermal desorption for both adsorbates. The proposed mechanism for this phenomenon is desorption induced by hot electron transfer from the substrate to the adsorbate. Enhanced lifetime of transient negative adsorbate due to stabilization by localized holes on PSi nanotips can explain the observed abnormally large PID efficiency on top of porous silicon.

Photoinduced desorption of Xe from porous Si following ultraviolet irradiation: evidence for a selective and highly effective optical activity.

Photoinduced desorption (PID) of Xe from porous silicon (PSi) following UV irradiation has been studied. A nonthermal, morphology, and wavelength dependent phenomenon with more than 3 orders of magnitude enhancement of Xe PID within pores over atoms adsorbed on top of flat surfaces has been recorded, displaying extraordinary large cross sections up to σ(Xe/PSi)=2×10(-15) cm(2). A long-lived, photoinduced, charge separated silicon-xenon complex is proposed as the precursor for this remarkable photodesorption process.

Xe interacting with porous silicon.

Thin films of porous silicon (PS), structurally characterized by HR-SEM, were studied using xenon Temperature Programmed Desorption (TPD) as a probe of its inner pores. Geometric hindrance of the depth desorbing population and multiple wall collisions result in a unique double-peak structure of the TPD curve. Surface-diffusion assisted adsorption mechanism into inner pores at 48 K is proposed as the origin of these unique TPD spectra. It is experimentally verified by mild Ne(+) sputtering prior to TPD which preferentially removes Xe population from the top surfaces. A pore-diameter limited desorption kinetic model that takes into account diffusion and pore depth well explains the governing parameters that determine the experimental observations. These results suggest that TPD may be employed as a highly sensitive, non-destructive surface area determination tool.