Formation of Au, Pt, and bimetallic Au–Pt nanostructures from thermal dewetting of single-layer or bilayer thin films

Abstract

Formation of Au, Pt, and bimetallic Au-Pt nanostructures by thermal dewetting of single-layer Au, Pt and bilayer Au-Pt thin films on Si substrates was systematically studied. The solid-state dewetting of both single-layer and bilayer metallic films was shown to go through heterogeneous void initiation followed by void growth via capillary agglomeration. For the single-layer of Au and Pt films, the void growth started at a temperature right above the Hüttig temperature, at which the atoms at the surface or at defects become mobile. Uniformly distributed Au (7 ± 1 nm to 33 ± 8 nm) and Pt (7 ± 1 nm) NPs with monodispersed size distributions were produced from complete dewetting achieved for thinner 1.7−5.5 nm-thick Au and 1.4 nm-thick Pt films, respectively. The NP size is strongly dependent on the initial thin film thickness, but less so on temperature and time. Thermal dewetting of Au-Pt bilayer films resulted in partial dewetting only, forming isolated nano-islands or large particles, regardless of sputtering order and total thin film thickness. The increased resistance to thermal dewetting shown in the Au-Pt bilayer films as compared to the individual Au or Pt layer is a reflection of the stabilizing effect that occurs upon adding Pt to Au in the bimetallic system. Energy dispersive X-ray spectroscopic analysis showed that the two metals in the bilayer films broke up together instead of dewetting individually. According to the X-ray diffraction analysis, the produced Au-Pt nanostructures are phase-segregated, consisting of an Au-rich phase and a Pt-rich phase.

Formation and Removal of Alloyed Bimetallic Au–Ag Nanoparticles from Silicon Substrates for Tunable Surface Plasmon Resonance

“…The morphology of both the undewetted Au­(2.6 nm)­Ag­(2.5 nm) (Figure a) and Ag­(2.3 nm)­Au­(2.3 nm) (Figure g) films shows bicontinuous structures, indicating Volmer–Weber growth in which thin film growth proceeds through the formation of nanoislands . Similar thin film morphologies have been reported for both Au and Ag films individually. At 80 °C (Figure b,h), both bilayer films show deepening of the grain boundaries and initiation of voids.…”

“…The thermal dewetting of single-layer Au and Ag along with Pt on SiO 2 /Si substrates has been studied in detail in our previous work. , It was found that void growth started right above the Hüttig temperature of the metal and complete dewetting into isolated NPs occurred at a temperature in between the Hüttig and Tammann temperatures, the temperatures at which the surface and bulk atoms in the metal become mobile, respectively. Considering the values of the Hüttig and Tammann temperatures for Ag (97 and 344 °C) and Au (128 and 396 °C), the effect of temperature on the dewetting of Au–Ag bilayer thin films was studied in the range of 80–450 °C at a fixed time of 30 min.…”

“…The NPs achieved from thermal dewetting of bilayer samples are much larger than the sizes reported in our previous work for Au or Ag single layers individually with similar thickness. For example, the diameters of Au NPs from thermal dewetting of 1.7 and 2.8 nm thick Au film are 7 ± 1 and 18 ± 4 nm, respectively, 21 and that of the Ag NPs from 2.6 nm thick Ag film is 16 ± 4 nm. 34 This strongly indicates that it is the NPs.…”

“…In addition, metal NPs trapped in a stationary liquid layer on the target surface can lead to plasma shielding and ultimately lower the laser ablation efficiency in liquids . Dewetting, including both pulsed laser-induced dewetting (PLiD) and thermal dewetting, of thin metallic films has recently been widely used to produce highly uniform monometallic , and bimetallic , NPs.…”

β-Ga2O3 Nanostructures: Chemical Vapor Deposition Growth Using Thermally Dewetted Au Nanoparticles as Catalyst and Characterization

“…Before sputtering, the phosphorous-doped n -type Si (100) wafers with a resistivity of 1–20 Ω cm (Wafer World Inc., West Palm Beach, FL, USA) were cleaned successively with acetone, ethanol, and methanol, and dried using high-purity N 2 gas (99.999%, Praxair). Details of thermal dewetting to make metal NPs were described previously [ 36 , 37 , 38 ]. Briefly, thermal dewetting of 2.9 nm thick Au films on Si substrates was carried out in vacuum (~2 × 10 −3 Torr) at 600 °C for 1 h.…”