Interfacial role in room-temperature diffusion of Au into Si substrates

Bal, Jayanta Kumar; Hazra, S.

doi:10.1103/physrevb.75.205411

Cited by 49 publications

(56 citation statements)

References 29 publications

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“…X-ray reflectivity ͑XRR͒ measurements of Ag nanolayers on differently pretreated Si͑001͒ substrates were carried out using a versatile x-ray diffractometer ͑VXRD͒ ͑D8 Discover, Bruker AXS͒ setup. 37 VXRD consists of a diffractometer with Cu source ͑sealed tube͒ followed by a Göbel mirror to select and enhance Cu K␣ radiation ͑ = 1.54 Å͒. The diffractometer has a two-circle goniometer ͓ −2͔ with quarter-circle Eulerian cradle as sample stage.…”

Section: Methodsmentioning

confidence: 99%

“…XRR technique 38,39 essentially provides an electron-density profile ͑EDP͒, i.e., in-plane ͑x − y͒ average electron density ͑͒ as a function of depth ͑z͒ in high resolution. 32,37 To see the evolution of EDP, XRR data for one set of samples were collected as a function of time after keeping that set at ambient conditions, while for other set of samples, XRR data have been collected just before and after the samples were in ultrahigh vacuum ͑UHV͒ conditions. X-ray diffraction ͑XRD͒ data around Ag͑111͒ and Ag͑002͒ peaks were collected as a function of time for the same set of samples that kept at ambient conditions for monitoring the evolution of crystallinity and/or epitaxy.…”

Section: Methodsmentioning

confidence: 99%

“…37 However, the oxide growth in the Ag-Si͑001͒ system is very slow compared to that in the Au-Si͑001͒ system 37 and covers only about 30% of the surface area. It is known that the Ag/Si interface is less reactive compared to the Au/Si interface, 42 which makes the former interface abrupt and probably slow down the diffusion of oxygen at the interface through Ag layer.…”

Section: Dewetting and Epitaxy: A Controlled Evolutionmentioning

confidence: 98%

“…41 For the analysis, each sample has been divided into a number of layers with roughness at each interface. 32,37 The EDPs obtained from the fitting of the data are shown in the inset of Fig. 1.…”

Section: Electron-density Profile and Its Evolutionmentioning

confidence: 99%

“…It is also known that this passivation is not stable for longer time in open air, even in the presence of overlayer ͑such as Au͒. 37 With time, passivated layer desorbs 9 and native oxide layer grows at the metal-semiconductor interface, 37 which can change the surface and interface energies, leading to a modification in the film growth. No study has been made so far to monitor such later stages of growth of Ag on Si, which is very important from the stability point of view and gives rise to the possibility of studying interesting growth transition.…”

Section: Introductionmentioning

confidence: 99%

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Time-evolution growth of Ag nanolayers on differently-passivated Si(001) surfaces

Bal

Hazra

2009

Phys. Rev. B

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The growth and evolution of Ag nanolayers on differently-passivated Si͑001͒ substrates at ambient condition have been studied. Initial compactness and smoothness of Ag nanolayer on the H-passivated Si͑001͒ surface are found better compared to those on the Br-passivated Si͑001͒ surface, which can be understood considering surface free energy and surface mobility of the passivated surfaces. As the time passes, the growth of dewetted three-dimensional ͑3D͒ islandlike structures ͑Volmer-Weber-type mode͒ from comparatively wetted Ag nanolayer ͑Stranski-Krastanov-type mode͒ is evident at ambient conditions. Such evolution of growth is through dewetting ͑related to the change in the interfacial energy due to the oxide growth͒, migration, and coalesce of Ag, which can even produce large epitaxial ͓Ag͑001͒/Si͑001͔͒ 3D islands on H-passivated Si͑001͒ surface. The growth rate, size, number density, and epitaxy/nonepitaxy of 3D islands are different for different passivated surfaces. These differences can be realized considering the growth time of oxide ͑i.e., instability of passivated surface͒, in-plane inhomogeneity of interfacial energy ͑i.e., inhomogeneous nature of passivation͒, and in-plane diffusion of Ag on the passivated surfaces.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Dewetting and Epitaxy: A Controlled Evolutionmentioning

confidence: 98%

Section: Electron-density Profile and Its Evolutionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Time-evolution growth of Ag nanolayers on differently-passivated Si(001) surfaces

Bal

Hazra

2009

Phys. Rev. B

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Terahertz Metasurface Modulators Based on Photosensitive Silicon

Zhou

et al. 2023

Laser & Photonics Reviews

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Metasurfaces solve the lack of materials in the terahertz (THz) band and control precisely the amplitude, phase, polarization, and transmission characteristics of THz waves, providing an effective way to realize THz functional devices. This article focuses on the design of THz metasurface modulators with a unit structure consisting of metal square rings, including resonance frequency, phase, and amplitude modulators. By embedding photosensitive semiconductor silicon (Si) in the unit structure, the unit structure is built from meta‐atom to molecularization model under the optical pumping condition, and the resonance frequencies are switched between high and low frequencies. The resonance frequency switchable characteristic is demonstrated using the equivalent LC oscillation circuit model, and the theoretical calculation results agree well with the simulations. Through theoretical calculations, the modulators achieve ultrafast switching times of less than 0.141 ps by the optical pumps, which have significant advantages in ultrafast THz modulators. By continuing to change the embedded position of the silicon in the unit structure, not only is a wide range of THz phase modulation achieved, but also multilevel modulation of the phase is realized. It is found that there is a strong relationship between the modulation depth and phase variation of THz waves, and a reasonable analysis is given. Further the amplitude modulator with a larger modulation depth (MD) is developed, and when the conductivity of photosensitive semiconductor silicon (σSi) reaches 2.5 × 106 S m−1, return loss (RL) is ≈0 dB, and the maximum MD reaches ≈100%; in order to gain insight into the nature of modulation, the modulation mechanism of THz waves under optical pumping conditions is analyzed. In addition, graphene‐based THz metasurface amplitude modulators are designed. When the depth of amplitude modulation is achieved by bias voltage modulation of the Fermi energy level of graphene, the maximum modulation amplitude is 23.42 dB, with a minimal modulation accuracy of 0.05 THz eV−1. In the article, the designed modulators have extremely excellent modulation performance. It has great potential applications in silicon‐based THz photonic devices, ultrahigh frequency electronic devices, high sensitivity sensors, and high‐precision imaging.

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Molecularization of Metasurfaces for Multifunctional Ultrafast All‐Optical Terahertz Waves

Zhou,

Qiu,

et al. 2024

Physica Status Solidi (a)

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Hybrid metasurfaces incorporated by active materials hold great promise for state‐of‐the‐art terahertz functional devices. However, it is still a major challenge to achieve ultrafast, dynamic, and multifunctional effective control of THz waves via hybrid metasurfaces. Herein, a modulator consisting of split rings and cut‐wires is first demonstrated, with an amplitude of −35.6 dB at 0.524 THz. By embedding semiconductor silicon into specified locations to form a hybrid metasurface, the ultrastrong connectivity of the silicon bridges leads to rapid optical molecularization. Under photoexcitation, the frequency tuning range is 26.7%, the phase shifting reaches 357.5°, and the maximal modulation depth is 94.54%. Taking advantage of the rapid relaxation of photocarriers in the silicon bridges, the ultrafast frequency switching is within 1400 ps. More interestingly, by changing the positions of the silicon bridges, the frequency tuning range is further promoted to 60%, the phase shifting is 353.5°, the modulation depth of 100% is achieved, and the full recovery time is 1600 ps. Furthermore, the underlying mechanism of the ultrafast tuning process is elucidated. This work demonstrates the feasibility of all‐optical‐controlled hybrid metasurface to achieve multifunctional dynamic modulation of THz waves, which has tremendous potential for applications in optical switching, signal processing, and frequency conversion.

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Interfacial role in room-temperature diffusion of Au into Si substrates

Cited by 49 publications

References 29 publications

Time-evolution growth of Ag nanolayers on differently-passivated Si(001) surfaces

Time-evolution growth of Ag nanolayers on differently-passivated Si(001) surfaces

Terahertz Metasurface Modulators Based on Photosensitive Silicon

Molecularization of Metasurfaces for Multifunctional Ultrafast All‐Optical Terahertz Waves

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