Low-Power Super-resolution Readout with Antimony Bismuth Alloy Film as Mask layer

Sb-Bi alloy flms are proposed as a new kind of super-resolution mask layer with low readout threshold power. Using the Sb-Bi alloy film as a mask layer and SiN as a protective layer in a read-only memory disc, the superresolution pits with diameters of 380 nm are read out by a dynamic setup, the laser wavelength is 780 nm and the numerical aperture of pickup lens is 0.45. The effects of the Sb-Bi thin film thickness, laser readout power and disc rotating velocity on the readout signal are investigated. The results show that the threshold laser power of super-resolution readout of the Sb-Bi mask layer is about 0.5 m W, and the corresponding carrier-to-noise ratio is about 20 dB at the film thickness of 50nm. The super-resolution mechanism of the Sb-Bi alloy mask layer is discussed based on its temperature dependence of reflection.     

Optical Recording Properties of Metal-Azo Dye as Recording Medium with Super-Resolution Near-Field Structure

A novel metallized azo dye has been synthesized. The absorption spectra of the thin film and thermal characteristic are measured. Static optical recording properties with and without the Bi mask layer super-resolution near-field structure （Super-RENS） of the metal-azo dye are investigated. The results show that the metal-azo dye film has a broad absorbance band in the region of 450-650 nm and the maximum absorbance wavelength is located at 603 nm. It is also found that the new metallized azo dye occupies excellent thermal stability, initiatory decomposition temperature is at 270℃ and the mass loss is about 48% in a narrow temperature region （15℃）. The complex refractive index N （N = n ＋ iκ） is measured. High refractive index （n = 2.45） and low extinction coefficient （κ = 0.2） at the recording wavelength 65Ohm are attained. Static optical recording tests with and without Super-RENS are carried out using a 65Ohm semiconductor diode laser with recording power of 7mW and laser pulse duration of 200ns. The AFM images show that the diameter of recording mark on the dye film with the Bi mask layer is reduced about 42%, compared to that of recorded mark on the dye film without Super-RENS. It is indicated that Bi can well performed as a mask layer of the dye recording layer and the metallized azo dye can be a promising candidate for recording media with the super-resolution near-field structure.     

Readout of super-resolution marks with Ti thin film

Using Ti as the super-resolution reflective film to replace the Al reflective layer in conventional read-only optical disk, the recording marks with a diameter of 380 nm and a depth of 50 nm are read out in a dynamic testing device whose laser wavelength is 632.8 nm and numerical aperture of the lens is 0.40. The optimum Ti thin film thickness is 18 nm and the corresponding signal-noise-ratio is 32 dB.     

Magnetostatic Coupling in Ba0.8Sr0.2TiO3/CoFe2O4 Magnetoelectric Composite Thin Films of 2-2-Type Structure

Ba0.8Sr0.2 TiO3/CoFe2O4 （BST/CFO） magnetoelectric composite thin films of 2-2-type structures are prepared onto Pt/Ti/SiO2/Si substrates by a sol-gel process and spin coating technique. The structure of the prepared thin film is substrate/BST/CFO/. . ./CFO/BST. Three CFO ferromagnetic layers are separated from each other by a thin BST layer. The upper CFO layer is magnetostatically coupled with the lower CFO layer. Subsequent scanning electron microscopy investigations show that the prepared thin films exhibit good morphologies and have a compact structure, and the cross-sectional mierographs clearly display a multilayered nanostructure of multilayered thin films. The composite thin films exhibit good magnetic and ferroelectric properties. The spacing between ferromagnetic layers can be varied by adjusting the thickness of intermediate BST layer. It is found that the strength of magnetostatic coupling has a great impact on magnetoelectric properties of composite thin film; that is, the magnetoelectric voltage coefficient of the composite thin film tends to increase with the decrease of pacing between two neighboring CFO ferromagnetic layers as a result of magnetostatic coupling effect.     

Multiple Scattering Effects of Ag Particles in Random Ag-SiN Film

A layer of 40nm-thick Ag-SiN film with Ag nano-particles embedded and distributed randomly in the SiN thin film were deposited by the method of radiant-frequency magnetron sputtering. Specimens orderly comprising a random Ag-SiN film and an optical phase change recording layer were exposed to a focused laser beam with wavelength of 69Ohm. It is shown that, with a random Ag-SiN layer deposited above the recording layer. Calculation by the finite difference time domain method of a 4Ohm-thick SiN film under a Gaussian beam irradiation has been carried out to simulate the near-field distribution in the film, which showed a huge local near-field intensity enhancement of about 200 times if small Ag particles with diameter of 6 nm were modelled inthe SiN film in the central region of the in cident laser spot.     

Optical Switch Formation in Antimony Super-Resolution Mask Layers Induced by Picosecond Laser Pulses

Sb is a classic material of a super-resolution near field structure （super-RENS） mask layer in which the optical switch formation is often realized by nanosecond laser pulse stimulation. We achieve fast and repeatable optical switching driven by picosecond laser pulses in a proper fluence range on Sb thin films. The optical properties of Sb thin films before and after switching are studied by surface-sensitive micro-area ellipsometry. The change of optical constants after switching is less than 2% in the whole visible range. The Sb mask layer is shown to be very promising for ultrafast super-resolution optical storage applications.     

Application of an Al-doped zinc oxide subcontact layer on vanadium-compensated 6H–SiC photoconductive switches

Al-doped Zn O thin film(AZO) is used as a subcontact layer in 6H–Si C photoconductive semiconductor switches(PCSSs) to reduce the on-state resistance and optimize the device structure. Our photoconductive test shows that the onstate resistance of lateral PCSS with an n+-AZO subcontact layer is 14.7% lower than that of PCSS without an n+-AZO subcontact layer. This occurs because a heavy-doped AZO thin film can improve Ohmic contact properties, reduce contact resistance, and alleviate Joule heating. Combined with the high transparance characteristic at 532 nm of AZO film, vertical structural PCSS devices are designed and their structural superiority is discussed. This paper provides a feasible route for fabricating high performance Si C PCSS by using conductive and transparent Zn O-based materials.     

High-Density Read-Only Memory Disc with Ag11In12Sb51Te26 Super-Resolution Mask Layer

A novel read-only memory (ROM) disc with an Ag11ln12Sb51Te26 super-resolution mask layer is proposed and investigated for the first time to our knowledge. The carrier-to-noise ratio of more than 40 dB could be obtained from small pits (380nm), which are below the readout resolution limit (400nm), in our dynamic setup with a wavelength of 632.8 nm and numerical aperture of 0.40. Dependences of carrier-to-noise ratio on readout power,readout velocity and film thickness are studied. The results show that the optimum film thickness is 20-50nm and the corresponding carrier-to-noise ratio is more than 40dB at readout power of 4mW and readout velocity of 2m/s in our experiment. The super-resolution readout mechanism for this ROM disc is also discussed.     

Amorphous/Crystalline （n-n） Si Heterojunction Photodetector Made by Q-Switched 0.532-mm Laser Pulses with Novel Technique

Amorphous/crystalline n-n-isotype Si heterojunetions are made by a pulsed Q-switched second harmonic generation Nd：YAG laser. The process includes melting and subsequently fast resolidification of a thin front layer of monocrystalline Si by laser pulses to create an amorphous layer （phase transition）. Different laser energy densities are used to form the amorphous layer on a monocrystalline Si substrate, the results of the electrical characteristics of the heterojunctions are dependent strongly on the laser energy density. Optoelectronic properties such as current-voltage, capacitance voltage, and spectral sensitivity are measured in a-Si/c-Si hereto junctions （in the absence of anti-reflecting coating and frontal grid contact） prepared by different laser energy densities. The built-in-potential values extracted from current-voltage measurements are close to the published results of （n-p） amorphous/crystalline hereto junction made by glow discharge and plasma enhanced chemical vapour deposition. Furthermore, examination of the formation of amorphous pattern on Si surface is carried out with the help of optical microscopy. Best photovoltaic performance is recognized to be at ,5.6 J/cm^2. The photodetector shows a wide spectral response, and the peak response is at 780nm. On the other hand, this peak is independent of laser energy.     

Hybrid mono-crystalline silicon and lithium niobate thin films [Invited]

The heterogeneous integration of silicon thin film and lithium niobate(LN) thin film combines both the advantages of the excellent electronics properties and mature micro-processing technology of Si and the excellent optical properties of LN,comprising a potentially promising material platform for photonic integrated circuits. Based on ion-implantation and wafer-bonding technologies, a 3 inch wafer-scale hybrid mono-crystalline Si/LN thin film was fabricated. A high-resolution transmission electron microscope was used to investigate the crystal-lattice arrangement of each layer and the interfaces. Only the H-atom-concentration distribution was investigated using secondary-ion mass spectroscopy. Highresolution X-ray-diffraction ω–2θ scanning was used to study the lattice properties of the Si/LN thin films. Raman measurements were performed to investigate the bulk Si and the Si thin films. Si strip-loaded straight waveguides were fabricated, and the optical propagation loss of a 5-μm-width waveguide was 6 d B/cm for the quasi-TE mode at1550 nm. The characterization results provide useful information regarding this hybrid material.     

Superresolution optical disk with a thermoreversible organic thin film

Recording and retrieving small marks far beyond the optical diffraction limit in a high-speed rotating phase-change optical disk have been investigated by use of a thermoreversible organic thin film as a superresolution mask layer. The organic thin film exhibited significant thermoreversibility and rapid response on laser irradiation. Recorded marks as small as 120 nm in length could be detected by a dynamic disk tester with a laser wavelength of 635 nm and a numerical aperture of 0.6.     

Super-resolution readout property of bismuth-doped antimony-based thin film as a functional mask for read-only memory

Bismuth-doped antimony-based (Sb_100?x Bi _x , x=2.46) thin films were presented as a functional mask for super-resolution readout of read-only memory (ROM). The pit size of the ROM was 390?nm, and super-resolution readout was realized on a dynamic tester with laser wavelength of 780?nm and the numerical aperture of the focusing objective lens of 0.45. The carrier-to-noise ratio (CNR) of 22?dB, readout threshold power of 0.8?mW and super-resolution readout cycles of 2×10⁴ was achieved. The influence of film thickness and readout power on CNR was investigated. The reflectivity and transmittance of the film with different temperature at wavelength of 780?nm were detected, and the super-resolution mechanism of the bismuth-doped antimony-based thin films as the functional mask layer was discussed.     

Fabrication and characteristics of a surface acoustic wave UV sensor based on ZnO thin films grown on a polycrystalline 3C-SiC buffer layer

Zinc oxide (ZnO) thin films were deposited onto a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) ultraviolet (UV) sensing using a magnetron sputtering system. X-ray diffraction (XRD) and photoluminescence (PL) spectra showed that the ZnO film grown on 3C-SiC/Si had a dominant c-axis orientation, a lower residual stress, and higher intensity of luminescence at 380 nm of ZnO thin film. The SAW resonator UV detector were fabricated on ZnO/Si structures with a 3C-SiC buffer layer. The SAW resonator exposed under UV illumination had a linear response with sensitivity of 85 Hz/(μW/cm²) in ZnO/3C-SiC/Si structures, as compared to 25 Hz/(μW/cm²) in ZnO/Si structures with UV intensity varied until 600 μW/cm².     

Micromachining of a thin film by laser ablation using femtosecond laser with masks

A gold thin film was machined by laser ablation using a femtosecond laser with mask patterns in the shape of lines and numbers. The patterns were successfully transferred with proper focusing and laser fluence. The optimal femtosecond laser fluence to keep the line width was about 5.2 mJ/cm² on the mask, and 99 mJ/cm² on the film. The processing resolution was 13 μm, and the narrowest line width was about 4 μm.     

Specific character of the 119Sn thin films growth on amorphous Si by the CBPLD method

The research of the ¹¹⁹Sn thin films growth on amorphous Si that is important for the multilayer periodical spin-tunnel nanostructures creation have been investigated in this paper. The ¹¹⁹Sn mono-isotopic thin films on the silicon substrates (100) had been received by crossed-beam pulsed laser deposition method (CBPLD). Similarly the [Fe/Si/Sn/Si] multilayer periodical structures have been deposited. The received samples were investigated by atomic-force microscopy, electronic microscopy and X-ray reflectometry methods. It has been established that at ¹¹⁹Sn film thickness up to 3 nm it is possible to received atomic-smooth surfaces with 0.5 nm roughness.     

In situ RHEED analysis of epitaxial Gd2O3 thin films grown on Si (001)

Epitaxial Gd₂O₃ thin films were successfully grown on Si (001) substrates using a two-step approach by laser molecular-beam epitaxy. At the first step, a ～0.8 nm thin layer was deposited at the temperature of 200 ^°C as the buffer layer. Then the substrate temperature was increased to 650 ^°C and in situ annealing for 5 min, and a second Gd₂O₃ layer with a desired thickness was deposited. The whole growth process is monitored by in situ reflection high-energy electron diffraction (RHEED). In situ RHEED analysis of the growing film has revealed that the first Gd₂O₃ layer deposition and in situ annealing are the critical processes for the epitaxial growth of Gd₂O₃ film. The Gd₂O₃ film has a monoclinic phase characterized by X-ray diffraction. The high-resolution transmission electron microscopy image showed all the Gd₂O₃ layers have a little bending because of the stress. In addition, a 5–6 nm amorphous interfacial layer between the Gd₂O₃ film and Si substrate is due to the in situ high temperature annealing for a long time. The successful Gd₂O₃/Si epitaxial growth predicted a possibility to develop the new functional microelectronics devices.     

用激光分子束外延在Si衬底上外延生长高质量的TiN薄膜

采用激光分子束外延技术,利用两步法,在Si单晶衬底上成功地外延生长出TiN薄膜材料.原子力显微镜分析结果显示, TiN薄膜材料表面光滑,在10 μm×10 μm范围内,均方根粗糙度为0842nm.霍耳效应测量结果显示,TiN薄膜在室温条件下的电阻率为36×10^-5Ω·cm,迁移率达到5830 cm²/V·S,表明TiN薄膜材料是一种优良的电极材料.X射线θ—2θ扫描结果和很高的迁移率均表明,高质量的TiN薄膜材料被外延在Si衬底 关键词： 激光分子束外延 TiN单晶薄膜 外延生长     

Ultra fast melting process in femtosecond laser crystallization of thin a-Si layer

In this paper, we investigated the mechanism of crystallization induced by femtosecond laser irradiation for an amorphous Si (a-Si) thin layer on a crystalline Si (c-Si) substrate. The fundamental, SHG, THG wavelength of a Ti:Sapphire laser was used for the crystallization process. To investigate the processed areas we performed Laser Scanning Microscopy (LSM), Transmission Electron Microscopy (TEM) and Imaging Pump-Probe measurements. Except for 267 nm femtosecond laser irradiation, the crystallization occurred well. The threshold fluences for the crystallization using 800 nm and 400 nm femtosecond laser irradiations were 100 mJ/cm² and 30 mJ/cm², respectively. TEM observation revealed that the crystallization occurred by epitaxial growth from the boundary surface between the a-Si layer and c-Si substrate. The melting depths estimated by Imaging Pump-Probe measurements became shallower when the shorter wavelength was used.     

Tungsten silicide formation by XeCl excimer-laser irradiation of W/Si samples

We report a study of the formation of tungsten silicide at the W-Si interface, induced by multipulse (up to 300 shots) XeCl excimer-laser irradiation of W(150 nm)/Si and W(500 nm)/Si samples. Laser fluences ranging from 0.6 to 1.8 J/cm² were used. After laser treatment the samples were examined by different diagnostic techniques: Rutherford backscattering spectrometry, X-ray scattering, resistometry, and surface profilometry. Numerical computations of the evolution and depth profiles of the temperature in the samples as a consequence of a single 30 ns laser pulse were performed as well. The results indicate that it is possible to obtain a tungsten silicide layer at the W-Si interface at quite low fluences. The layer thickness increases with the number of laser pulses. Complete reaction of the 150 nm thick W film with silicon was obtained at the fluence of 1.2 J/cm² between 30 and 100 laser pulses and at 1.5 J/cm² after 30 laser pulses. The sheet resistance of these silicides was 5–10 . At the used fluences for the 500 nm thick W film only the onset of silicide synthesis at the W-Si interface was observed.