We have heteroepitaxially deposited compositionally graded (Ba1−xSrx)TiO3 (BST) thin films with increasing x from 0.0 to 0.25 on (100)-oriented MgO substrates using pulsed-laser deposition. The compositional gradients along the depth in the graded films were characterized by Rutherford backscattering spectroscopy. By using surface interdigital electrodes, the planar dielectric response of epitaxial graded BST films was measured as a function of frequency, temperature, and dc applied voltage. At room temperature, the dielectric constant of the graded BST film was about 450 with a dielectric loss, tan δ of 0.007 at 100 kHz. Measurements varying the dc bias voltage showed hysteresis of the dielectric response and a tunability of 25% at an applied electric field of 80 kV/cm. The graded BST films undergo a diffuse phase transition with a broad and flat profile of the capacitance versus temperature. Such behavior of the dielectric response in graded BST films is attributed to the presence of the compositional and/or residual strain gradients in the epitaxial graded films. With such a graded structure, it is possible to a build a dielectric thin-film capacitor with a low-temperature dependence of the capacitor over a broad temperature regime.

Pb 0.9 La 0.1 Ti 0.975 O 3 ͑PLT10͒ thin films were deposited on SiO 2 /Si(100) substrates coated with a ZrO 2 buffer layer. Studies by x-ray diffraction and scanning electron microscopy reveal that the ZrO 2 film consists of both tetragonal and monoclinic phases, with the tetragonal phase being the dominant one. The PLT10 film has a perovskite structure and the grains in the film have a rather uniform size of about 50 nm. By using interdigital transducer ͑IDT͒ electrodes the in-plane electrical properties, hysteresis loop, and pyroelectric coefficient of the PLT10 film were measured. The dielectric constant and loss factor vary only slightly with frequency in the range 10 3 -10 6 Hz, with the loss factor being less than 0.01 over the entire range. The leakage current density is lower than 2ϫ10 Ϫ8 A/cm 2 at a bias field of 5 kV/cm. The remnant polarization and coercive field are 12.6 C/cm 2 and 9.93 kV/cm, respectively. The film exhibits a reasonably high pyroelectric coefficient (95 C/m 2 K) after it has been poled by applying 120 V ac at 0. [1][2][3][4] These films have potential applications in a variety of devices including nonvolatile memories, optical switches, and infrared detectors. 5,6 Lead zirconate titanate ͑PZT͒ films were successfully deposited on ZrO 2 -passivated silicon substrates and were poled parallel to the film surface to give in-plane polarization. 7 Micromachined ultrasound arrays based on inplane polarized PZT films showed a 30 dB improvement in sensitivity. 8 In this work, PLT10 thin films were deposited on silicon substrates coated with ZrO 2 buffer layers. We investigated the in-plane electrical and pyroelectric properties of the PLT10 thin films by using interdigital transducer ͑IDT͒ electrodes. The films were found to exhibit good dielectric, ferroelectric, and pyroelectric properties in this in-plane configuration.The ZrO 2 buffer layer and PLT10 thin film were prepared by the metal-organic decomposition ͑MOD͒ method. A precise control of the solution concentration was important to produce high-quality, smooth, and crack-free films. To prepare the ZrO 2 solution, zirconium n-propoxide was added to distilled 2-methoxyethanol; the mixture was stirred at 120°C for 1 hr until the associated water was removed. After cooling to room temperature, the solution was filtered and a suitable amount of 2-methoxyethanol was added so as to give a concentration of 0.3 M. The raw materials for preparing PLT10 thin films were lead acetate trihydrate, lanthanum nitrate, and titanium isopropoxide. 2-methoxyethanol was used as the solvent. The preparation procedure of the metalalkoxide precursor solution has been described in detail elsewhere. 9,10 The substrate was a ͑100͒-oriented n-type silicon wafer coated with a 5.46-m-thick SiO 2 layer. ZrO 2 layers were deposited on the substrate by spin coating at 2500 rpm for 25 s. Each layer was pyrolyzed in O 2 at 600°C for 10 min. After depositing 20 layers of ZrO 2 , the resulting film was annealed in O 2 at 600°C for 1 hr. Another 20 layers of PLT10 were t...

Polycrystalline silicon (polysilicon) airbridges coupled to log-periodic and bow-tie planar antennas have been fabricated for mid-infrared radiation detection. The detectors in thermocouple and bolometer modes exhibit a higher electrical responsivity than previously reported metal based antenna-coupled thermal detectors. Measurements made at 10.2 μm wavelength indicate that the linearly polarized antennas have an on-axis cross-polarization ratio of about −4.5 dB and the pattern in the free-space side has a directivity of approximately 5–9 dB. The coupling efficiency is about 15%. Frequency responses for modulated optical signals agree with thermal transport models.

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Thermal dissociation process of hydrogen atoms in plasma-enhanced chemical vapor deposited silicon nitride films J. Appl. Phys. 84, 5243 (1998); 10.1063/1.368813Infrared and x-ray photoelectron spectroscopy studies of as-prepared and furnace-annealed radio-frequency sputtered amorphous silicon carbide films