Quantum Engineering of Atomically Smooth Single-Crystalline Silver Films

Abstract

There is a demand for ultra low-loss metal films with high-quality single crystals and perfect surface for nanophotonics and quantum information processing. Many researches are devoted to alternative materials, but silver is by far theoretically the most preferred low-loss material at optical and near-IR frequencies. Usually, epitaxial growth is used to deposit single-crystalline silver films, but they still suffer from unpredictable losses and well-known dewetting effect that strongly limits films quality. Here we report the two-step approach for e-beam evaporation of atomically smooth single-crystalline metal films. The proposed method is based on the thermodynamic control of film growth kinetics at atomic level, which allows depositing state-of-art metal films and overcoming the film-surface dewetting. Here we use it to deposit 35–100 nm thick single-crystalline silver films with the sub-100pm surface roughness and theoretically limited optical losses, considering an ideal material for ultrahigh-Q nanophotonic devices. Utilizing these films we experimentally estimate the contribution of grain boundaries, material purity, surface roughness and crystallinity to optical properties of metal films. We demonstrate our «SCULL» two-step approach for single-crystalline growth of silver, gold and aluminum films which open fundamentally new possibilities in nanophotonics, biotechnology and superconductive quantum technologies. We believe it could be readily adopted for the synthesis of other extremely low-loss single-crystalline metal films.

Ultrafast quantum photonics enabled by coupling plasmonic nanocavities to strongly radiative antennas

“…We performed an experiment using a deterministically assembled [24] NPA [ Fig. 1(a)] formed by a crystalline silver nanocube and an epitaxial SCULL (single-crystalline continuous ultrasmooth low-loss low-cost) silver film [25]. A nanodiamond with 17 nm height hosting a single nitrogen-vacancy (NV) center was first identified on a glass coverslip substrate, optically characterized, then transferred to the silver film by means of an atomic force microscope tip and coated with a 5 nm thick alumina spacer layer.…”

“…The metal is optically characterized by its plasma frequency ω p and its plasmon absorption rate γ ohm . For a nanoantenna made of crystalline silver, we take γ ohm = 2π × 2 THz and ω p = 2π × 2200 THz [25,26]. We assume that the smaller cavity mode has an effective volume V 1 , while the larger antenna mode has a volume V 2 .…”

A wideband cryogenic microwave low-noise amplifier

“…Each resonator was coupled to a single qubit. The sample was made at the BMSTU Nanofabrication Facility (FMN Laboratory, FMNS REC, ID 74300) using Al technology [29,30]. The X-mon qubit was made of two Al/Al x O y /Al parallel Josephson junctions forming a SQUID-type structure coupled to the main ground plane.…”

SERS-Active Substrates Nanoengineering Based on e-Beam Evaporated Self-Assembled Silver Films

“…However, such films have limited applications due to low thermal conductivity, leading to SERS substrate degradation when exposed to exciting laser radiation power above several mW. By experimentally controlling evaporation process recipe parameters, it becomes possible to obtain continuous noble metal thin films with a well-controlled morphology down to atomically flat surfaces, crystalline structure, electrical and optical parameters [41][42][43][44][45][46][47].…”