Single-crystalline silver film grown on Si (100) substrate by using electron-gun evaporation and thermal treatment

Abstract

The authors demonstrate a simple method to fabricate ultrasmooth single-crystalline silver (Ag) films with high reflectivity and low plasmonic damping. The single-crystalline Ag thin film on the clean Si (100) substrate is first deposited by electron-gun evaporator and then treated by rapid thermal annealing (RTA) to improve its quality. The crystal structure and surface morphology are characterized by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Optical constants of the prepared films are extracted by fitting the measured reflectivity spectra with the Drude model. These results show that the Ag film with 340 °C RTA has the best film quality, including small surface roughness of 0.46 nm, a sharp x-ray diffraction peak with FWHM of 0.3°, and lowest damping in the visible and near-infrared wavelength regime. Therefore, our method is not only cost-effective but also useful for fabricating metal-based plasmonic and nanophotonic devices.

Realization of UV Plasmonic Nanolasers With Extremely Small Mode Volume

“…We placed ZnO nanowires on the single-crystalline Ag film [25] with 7 nm thick and 12 nm thick SiO 2 spacer layers, respectively. Because the wavelength corresponds to the plasma frequency of the bulk Ag is 138 nm, Ag is the material typically used in the visible and near-infrared regimes.…”

“…Before loading the silicon substrate into the E-gun evaporator chamber, a standard RCA cleaning process (along with dipping in the HF:H 2 O [1:100] solution) was performed to remove the oxidation layer. The 200 nm thick Ag thin film was evaporated on the (100) intrinsic silicon substrate under a 1×10 −6 Torr environment, and was then annealed at 340°C for 60 s in the nitrogen-flowing environment to flatten the surface roughness and rearrange the Ag atoms to form an atomically flat, single-crystalline metal film [25]. According to this procedure, the root-mean-square (RMS) roughness of the Ag film could be as low as about 0.5 nm.…”

“…Aluminum and silver are better candidate metals for generating low-loss SPs to realize UV plasmonic nanolasers [25]- [27]. Zhang et al recently demonstrated the feasibility of UV plasmonic nanolasers by using GaN as a gain medium and aluminum to generate SPs.…”

“…The large exciton binding energy and oscillator strength of ZnO are also beneficial to the coupling between the excitons and SPs. Furthermore, the atomically flat, single-crystalline Ag [25] is applied to lower the SP scattering loss and metal absorption loss. As a consequence, we focus on investigating the influence of the dielectric (SiO 2 ) spacer thickness on the ZnO plasmonic nanolaser's performance on silver, and attempt to isolate an optimized structure for overcoming the bending-back effect in ZnO UV plasmonic nanolasers.…”

Design of Bottom-Emitting Metallic Nanolasers Integrated With Silicon-On-Insulator Waveguides

“…This SiN x layer has two major functions: one is served as the a current-blocking layer to prevent the leakage current, and the other is served as a part of optical waveguide shell to reduce the optical field leak to the silver, which would result in a serious metal absorption loss [23]. The silver can provide several functionalities in the nanolaser, including the cavity boundary for optical mode confinement [24], shielding from crosstalk among lasers, the electrical contacts and, more importantly, an efficient heat sink.…”