Microfabrication of solenoid-type RF SMD chip inductors with an Al2O3 core

We investigated micron size, high-performance, and solenoid-type radio-frequency surface-mounted device (SMD) chip inductors with a low-loss Al₂O₃ core for a GHz drive microwave circuit application. Copper coils with a diameter of 27 μm were used and the chip inductors fabricated in this study are 0.86 × 0.46 × 0.45 mm³. The high-frequency characteristics of the inductance (L), quality factor (Q), and impedance (Z) of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). The developed inductors have a self-resonant frequency of 3.7–5.2 GHz and exhibit L of 15–34 nH. The inductors have Q of 38–49 over the frequency ranges of 900 MHz–1.7 GHz. The calculated data obtained from the equivalent circuit and the derived equation of Q described the high-frequency data of L, Q, and Z of the inductors developed quite well.     

Development and characteristics of solenoid-type SMD RF chip inductors

Simple, solenoid-type surface-mounted device (SMD) chip inductors utilizing low-loss Al₂O₃ core materials for a radio-frequency (RF) drive microwave circuit application were developed. The SMD chip inductors were fabricated with five different specifications, namely, 0.86 × 0.46 × 0.45, 1.0 × 0.5 × 0.5, 1.5 × 1.0 × 0.7, 2.1 × 1.5 × 1.0, and 2.4 × 2.0 × 1.4 mm³. Copper coils with diameters in the range of 27–40 μm were used. The frequency characteristics of the inductance (L), quality factor (Q), and impedance of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 12 have L of 34–270 nH, exhibit a self-resonant frequency (SRF) of 3.7–0.75 GHz, and have Q of 40–70 over the frequency ranges of 200 MHz–1.2 GHz. The L of inductors increases and the SRF decreases with increasing the size of inductors. From the experimental results, it was concluded that the high-frequency data calculated from the equivalent circuit and the derived equation of Q described quite well the experimental data of the developed inductors.     

Characteristics of thin film inductors using magnetic multilayered films with ceramic intermediate layers

Circular spiral thin film inductors were fabricated using as-deposited magnetic multilayered films with ceramic intermediate layers, and a thin film inductor with a single magnetic layer was also fabricated for comparison. The magnetic multilayered films have good soft magnetic properties and high resistivity thus can decrease the eddy current loss. Employing the magnetic multilayered films, we got a higher quality factor (>30) and better inductor characteristics as compared with the inductor with a single magnetic layer, such as a high operating frequency (>80 MHz) without decreasing the inductance.     

Fabrication of Gd0.5Sr0.5CoO3 film for SOFC cathode by pulsed laser deposition

Gd_0.5Sr_0.5CoO₃ (GSCO) film has been fabricated by pulsed laser deposition (PLD) to be used as the cathode of the solid oxide fuel cell (SOFC). The GSCO thin film obtained has a columnar crystalline structure so that it will have a high permeation property. The PLD technique has been found suitable for growing a film of complex composition because of its good control of stoichiometry and thus for fabricating a GSCO film used as the cathode of the SOFC. The GSCO film has been studied for porosity electrical conductivity and power density. The GSCO film grown at a substrate temperature of 1100 K and oxygen gas pressure of 100 Pa has high electrical conductivity which is 820 S cm^− 1 at 973 K with post annealing at a rather low temperature (1000 K). This value is higher than that of the GSCO film prepared by RF-sputtering with post annealing at a higher temperature (1273 K).     

Comparative study on structural and optical properties of ZnO thin films prepared by PLD using ZnO powder target and ceramic target

Zinc oxide thin films have been obtained in O₂ ambient at a pressure of 1.3 Pa by pulsed laser deposition (PLD) using ZnO powder target and ceramic target. The effect of temperature on structural and optical properties of ZnO thin films was investigated systematically by XRD, SEM, FTIR and PL spectra. The results show that the best structural and optical properties can be achieved for ZnO thin film fabricated at 700 °C using powder target and at 400 °C using ceramic target, respectively. The PL spectrum reveals that the efficiency of UV emission of ZnO thin film fabricated by using powder target is low, and the defect emission of ZnO thin film derived from Zn_i and O_i is high.     

Voltage–current and voltage–flux characteristics of asymmetric high TC DC SQUIDs

We report measurements of transfer functions and flux shifts of 20 on-chip high T_C DC SQUIDs half of which were made purposely geometrically asymmetric. All of these SQUIDs were fabricated using standard high T_C thin-film technology and they were single layer ones, having 140 nm thickness of YBa₂Cu₃O_7?x film deposited by laser ablation onto MgO bicrystal substrates with 24° misorientation angle. For every SQUID the parameters of its intrinsic asymmetry, i.e., the density of critical current and resistivity of every junction, were measured directly and independently. We showed that the main reason for the on-chip spreading of SQUIDs’ voltage–current and voltage–flux characteristics was the intrinsic asymmetry. We found that for SQUIDs with a relative large inductance (L > 120 pH) both the voltage modulation and the transfer function were not very sensitive to the junctions asymmetry, whereas SQUIDs with smaller inductance (L ? 65–75 pH) were more sensitive. The results obtained in the paper are important for the implementation in the sensitive instruments based on high T_C SQUID arrays and gratings.     

Chemical solution processing and properties of Sr2FeMoO6 thin films

Crack-free and oriented Sr₂FeMoO₆ (SFMO) thin film with double perovskite structure has been fabricated by the chemical solution deposition (CSD) method. A homogeneous and stable SFMO precursor solution was successfully prepared by controlling the reaction of starting metal-organic compounds in a mixture solvent of 1-propanol and 2-methoxyethanol. SFMO thin films with c-axis preferred orientation could successfully be synthesized on MgO (0 0 1) and SrTiO₃ (0 0 1) substrates by optimizing the several processing conditions. SFMO thin film prepared on SrTiO₃ (0 0 1) showed a magnetoresistance effect at a low magnetic field.     

An infrared pyroelectric detector improved by cool isostatic pressing with cup-shaped PZT thick film on silicon substrate

In this paper, we presented a new pyroelectric detector with back to back silicon cups and micro-bridge structure. The PZT thick film shaped in the front cup was directly deposited with designed pattern by electrophoresis deposition (EPD). Pt/Ti Metal film, which was fabricated by standard photolithography and lift-off technology, was sputtered to connect the top electrode and the bonding pad. The cold isostatic press (CIP) treatment could be applied to improve the pyroelectric properties of PZT thick film. The infrared (IR) properties the CIP-optimized detector were measured. The voltage responsivity (R_V) was 4.5 × 10² V/W at 5.3 Hz, the specific detectivity (D^*) was greater than 6.34 × 10⁸ cm Hz^1/2 W⁻¹ (frequency > 110 Hz), and the thermal time constant was 51 ms, respectively.     

A novel Si-based photodetector with flat-top and steep-edge spectral response

To meet the requirement of the dense wavelength-division-multiplexed (DWDM) system and optoelectronic integrated circuit, we design a Si-Based InGaAs photodetector, which is fabricated by bonding InGaAs/InP photodetector on a Si-Based dielectric film Fabry–Perot filter. The photodetector can exhibit an extremely good flat-top and steep-edge spectral response through designing the structure of Si-Based dielectric film Fabry–Perot filter. The simulation result of phtodetector demonstrates that the spectral response linewidth, ?at-top and steep-edge characteristics of these photodetectors are suitable to be used in 50 GHz, 100 GHz, 200 GHz DWDM system.     

Microstructures and nano mechanical properties of the metal tungsten film

The W film was prepared on 1045 steel by magnetron sputtering, with the thickness of 2 μm, its surface and cross-section morphologies were investigated with SEM, and the phase structure was analyzed with XRD. X-ray stress determinator was utilized to measure its residual stress, and the nano-hardness and elastic modulus of the film were surveyed by nano-indentation tester. The results show that the surface of W film is very compact and smooth; the particles arranged regularly, the granularity of the thin film is about 1 μm. The microcracks, cavities and desquamation were not found in the film and interface, and the bonding between the W film and substrate is well. The XRD results showed that the W film had a body-centered cubic structure, the lattice constant: a = 0.316 nm, the growth preferred orientations are (1 1 0) and (2 2 0). The compressive stress (−169 MPa) was found on the surface. The average nano-hardness and elastic modulus of W film are 15.22 GPa, 176.64 GPa, respectively, and the mechanical properties of W film are well.     

Investigation of reduced graphene oxide effects on ultra-violet detection of ZnO thin film

The reduced graphene oxide (rGO) incorporated ZnO thin films were fabricated by dip-coating method. The Raman and FT-IR spectra of 0.075 wt% incorporated composite film showed reduction of GO in composite film. The transmittanceProd. Type: FTP spectra have shown that rGO incorporation increase the visible light absorption of ZnO thin film while the calculated band gaps of samples were decreased from 3.28 to 3.25 eV by increasing the rGO content. The linear trend of I–V curve suggests an ohmic contact between ZnO and rGO. Besides, it was found that by increasing the rGO content, the electrical resistivity was decreased from 4.32×10² Ω cm for pure ZnO film to 2.4×10¹ Ω cm for 0.225 wt% rGO incorporated composite film. The composite photodetectors not only possessed a desirable UV photosensitivity, but also the response time of optimum sample containing 0.075 wt% rGO was reduced to about one-half of pure ZnO thin film. Also, the calculated signal to noise (SNR) showed that highly conductive rGO in composite thin films facilitate the carrier transportation by removing the trapping centers. The mechanism of photoresponsivity improvement of composite thin films was proposed by carrier transportation process.     

Low-cost micro-lens arrays fabricated by photosensitive sol–gel and multi-beam laser interference

In this paper, we introduce a low-cost approach for fabricating micro-lens arrays that is based on photosensitive sol–gel and multi-beam laser interference. UV photosensitive ZrO₂ gel films are prepared with Zr(O(CH₂)₃CH₃)₄ and BzAcH as the precursor and chemical modifier, respectively. With UV laser irradiation via different dose, nonlinear photodecomposition occurs in this film. Large scale 2D micro lens arrays with the sizes of 830 nm × 830 nm and 280 nm × 280 nm are fabricated by four-beam laser interference. The surface profile modeling shows that the micro lens is plano convex lens, and the effective focal lengths are 812.0 nm and 317.6 nm, respectively.     

Preparation of cadmium stannate films by spray pyrolysis technique

Cadmium stannate thin films were prepared by spray pyrolysis technique using cadmium acetate and tin(II) chloride precursors at substrate temperatures 450 °C and 500 °C. XRD pattern confirms the formation of orthorhombic (1 1 1) cadmium stannate phase for the film prepared at substrate temperature of 500 °C, whereas, films prepared at 450 °C are amorphous. Film formation does not occur at substrate temperature from 300 to 375 °C. SEM images reveal that the surface of the prepared Cd₂SnO₄ film is smooth. The average optical transmittance of ∼86% is obtained for the film prepared at substrate temperature of 500 °C with the film thickness of 400 nm. The optical band gap value of the films varies from 2.7 to 2.94 eV. The film prepared at 500 °C shows a minimum resistivity of 35.6 × 10⁻⁴ Ω cm.     

Microstructures and soft magnetic properties of as-deposited Fe–Sm–O thin films

The influences of O₂ partial pressure on saturation magnetization, coercivity and effective permeability of the as-deposited Fe–Sm–O thin films, which were fabricated by RF magnetron reactive sputtering method, were investigated. The nanocrystalline Fe_83.4Sm_3.4O_13.2 thin film fabricated at O₂ partial pressure of 5% exhibited the best magnetic softness with a saturation magnetization of 1.43 MA/m, coercivity of 65.2 A/m and effective permeability of about 2600 in the frequency range from 0.5 to 100 MHz. The electrical resistivity of Fe_83.4Sm_3.4O_13.2 was 130 μΩ cm. The microstructures and electrical resistivity were investigated in this work.     

Transparent CdO/n-GaN(0001) heterojunction for optoelectronic applications

Undoped CdO films were prepared by sol–gel method. Transparent heterojunction diodes were fabricated by depositing n-type CdO films on the n-type GaN (0001) substrate. Current–voltage (I–V) measurements of the device were evaluated, and the results indicated a non-ideal rectifying characteristic with I_F/I_R value as high as 1.17×10³ at 2 V, low leakage current of 4.88×10⁻⁶ A and a turn-on voltage of about 0.7 V. From the optical data, the optical band gaps for the CdO film and GaN were calculated to be 2.30 eV and 3.309 eV, respectively. It is evaluated that interband transition in the film is provided by the direct allowed transition. The n-GaN (0001)/CdO heterojunction device has an optical transmission of 50–70% from 500 nm to 800 nm wavelength range.     

Fast and wide-band response infrared detector using porous PZT pyroelectric thick film

Porous lead zirconate titanate (PbZr_0.3Ti_0.7O₃, PZT30/70) thick films and detectors for pyroelectric applications have been fabricated on alumina substrates by screen-printing technology. Low temperature sintering of PZT thick films have been achieved at 850 °C by using Li₂CO₃ and Bi₂O₃ sintering aids. The microstructure of PZT thick film has been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties were measured using HP 4284 at 1 kHz under 25 °C. The permittivity and loss tangent of the thick films were 94 and 0.017, respectively. Curie temperature of PZT thick film was 425 °C as revealed by dielectric constant temperature measurement. The pyroelectric coefficient was determined to be 0.9 × 10⁻⁸ Ccm⁻² K⁻¹ by dynamic current measurement. Infrared detector sensitive element of dual capacitance was fabricated by laser directly write technology. Detectivity of the detectors were measured using mechanically chopped blackbody radiation. Detectivity ranging from 1.23 × 10⁸ to 1.75 × 10⁸ (cm Hz^1/2 W⁻¹) was derived at frequency range from 175.5 Hz to 1367 Hz, and D^*’s −3 dB cut-off frequency bandwidth was 1.2 kHz. The results indicate that the infrared detectors based on porous thick films have great potential applications in fast and wide-band frequency response conditions.     

Novel optical add-drop multiplexer based on dual racetrack resonators

In this paper, we designed and fabricated a four-channel optical add-drop multiplexer (OADM) based on dual racetrack resonators. The size of the fabricated device is only 2400 μm × 500 μm. The fabricated device can effectively and perfectly realize the signals upload and download. The free spectral range (FSR) of OADM is about 15.2 nm. We take the spectral responses near 1555 nm as an example. When the device acts as an optical drop multiplexer, the minimum insertion loss is 4.481 dB and the maximum extinction ratio is 31.931 dB. The maximum adjacent channels crosstalk is -9.845 dB. When the device acts as an optical add multiplexer, the minimum insertion loss is 0.944 dB and all of the extinction ratios are bigger than 25 dB. The maximum crosstalk is -16.531 dB which indicates the crosstalk can be neglected.     

Texture and strain in CoPt/Ag nanocomposite films

The texture and microstrain in CoPt/Ag nanocomposite films is monitored as a function of film thickness. Perpendicular anisotropy due to (0 0 1) texturing is achieved by annealing films with thickness below 15 nm at 600°C. As a function of film thickness δ the texture evolves from weak (0 0 1) below 9 nm to strong (0 0 1) at δ=12 nm which deteriorates rapidly above 15 nm and evolves to (1 1 1) above 40 nm. The strain is minimized in the range of film thickness where the (0 0 1) texturing is optimum indicating a texturing mechanism related to the reduction of mechanical strain energy.     

Strain study of gold nanomaterials as HR-TEM calibration standard

This work presents the use of high resolution electron microscopy (HREM) and geometric phase analysis (GPA) to measure the interplanar spacing and strain distribution of three gold nanomaterials, respectively. The results showed that the {1 1 1} strain was smaller than the {0 0 2} strain for any kind of gold materials at the condition of same measuring method. The 0.65% of {1 1 1} strain in gold film measured by HREM (0.26% measured by GPA) was smaller than the {1 1 1} strains in two gold particles. The presence of lattice strain was interpreted according to the growth mechanism of metallic thin film. It is deduced that the {1 1 1} interplanar spacing of the gold thin film is suitable for high magnification calibration of transmission electron microscopy (TEM) and the gold film is potential to be a new calibration standard of TEM.     

Oxidation of ultra-thin Ti films on Mo(100): Soft X-ray photoelectron spectroscopy study

Titanium oxide films grown on Mo(100) have been investigated by low-energy electron diffraction (LEED) and soft X-ray photoelectron spectroscopy (PES). The film was grown by Ti deposition on Mo(100) and subsequent oxidation of the film by 12 L of O₂ exposure at room temperature. As the film was annealed at 700–1000 °C, the film in which the Ti atoms were in a Ti³⁺ oxidation state was formed. As the film was annealed at 1100–1500 °C, the oxidation state of Ti in the film was converted to Ti²⁺. The valence electronic structure of the film was measured under the condition that the emission from the Mo substrate was minimized due to a Cooper minimum of the Mo 4 d photoionization cross sections (hν = 100 eV). It was found that the Ti 3 d band in normal-emission spectra was increased in intensity when the film was annealed at 1100–1500 °C. As the film was annealed at 1300 °C for 10 s and 20 s, the film-covered Mo(100) gave (2 × 2) and (4 × 1) LEED patterns, respectively. The two-dimensional band structure of the (2 × 2) system was investigated by angle-resolved PES, and it was found that the film with a (1 × 1) periodicity with respect to the Mo(100) substrate existed in the (2 × 2) system.