Johannes Franciscus Maria Cillessen

Epitaxial PbTiO3 thin films grown by organometallic chemical vapor deposition

Epitaxial PbTiO3 layers have been grown on (001)SrTiO3 substrates by organometallic chemical vapor deposition using the precursors titanium‐iso‐propoxide and tetra‐ethyl‐lead. The growth temperature for these films was around 700 °C. The epitaxial nature of c‐axis‐oriented PbTiO3 is confirmed by Rutherford backscattering spectrometry, x‐ray diffraction, including pole figure analysis, and high‐resolution electron microscopy (HREM). With HREM twinning has been observed.

Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors

The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breaches this boundary. To enhance the response to the pH of the electrolyte, a self-assembled monolayer has been used as a top gate dielectric. The sensitivity scales linearly with the ratio between the top and bottom gate capacitances. The sensitivity of our ZnO ISFET of 22 mV/pH is enhanced by more than two orders of magnitude up to 2.25 V/pH.

Structural and electrical characterization of heteroepitaxial lead zirconate titanate thin films

PbZrxTi1−xO3 films have been grown heteroepitaxially onto (001)SrTiO3 and SrRuO3/(001)SrTiO3 by organometallic chemical vapor deposition. As a start, the microstructure of PbZrxTi1−xO3 films on (001)SrTiO3 was studied as a function of the zirconium fraction, x. Rutherford backscattering spectrometry, including channeling experiments, and transmission electron microscopy have shown that the microstructure is dominated by the crystal structure of the PbZrxTi1−xO3. In the case of tetragonal PbZrxTi1−xO3 the films may contain a‐axis oriented regions. These regions have not been observed for films with a composition giving a rhombohedral unit cell. Despite the rather large mismatch of rhombohedral PbZrxTi1−xO3 with the (001)SrTiO3, values as low as 4% for the minimum channeling yield have been obtained. For a rhombohedral film the ferroelectric properties have been measured. To this end a single crystalline PbZr0.8Ti0.2O3 film was grown onto (001)SrTiO3 provided with a heteroepitaxial SrRuO3 electrode grown by...

Field dependent permittivity in metal‐semiconducting SrTiO3 Schottky diodes

The field dependence of the dielectric constant of SrTiO3 is investigated using the capacitance versus bias voltage characteristics of various metal‐SrTiO3:Nb Schottky diodes. The relative dielectric constant is shown to decrease one order of magnitude for electric fields ranging from 0.1 to 10 MV/cm. At low fields the permittivity follows the Curie–Weiss law, whereas at fields larger than 500 kV/cm the permittivity is nearly temperature independent. At high doping densities the field dependent permittivity gives rise to a reduction of the depletion width of the Schottky diode.

Pulsed laser deposition of heteroepitaxial thin Pt films on MgO(100)

Abstract Pt thin films were deposited on MgO(100) using pulsed laser ablation deposition. The deposited films grow epitaxially with a Pt(111) X-ray diffraction (XRD) intensity less than 0.5% of that of the Pt(200) reflection in the films. The layer formation was observed to proceed via coalescence growth of (100)-oriented Pt islands. The layers obtained were remarkably smooth and without voids above a critical layer thickness which appeared to depend strongly on the deposition temperature. Rutherford backscattering spectrometry measurements and XRD pole figures revealed a complete alignment between the in-plane lattice vectors of Pt and MgO which suggests heteroepitaxial growth. The latter was confirmed using high resolution transmission electron microscopy.

Texture analysis of smooth in situ laser ablated YBa sub 2 Cu sub 3 O sub 7 thin films on (100) SrTiO sub 3

The texture of YBa2Cu3O7 thin films on (100) SrTiO3, grown by in situ laser ablation, was investigated by x‐ray diffraction. The surface morphology is smooth with only 105 cm−2 particulates of about 0.1 μm in diameter. High‐resolution x‐ray diffraction shows that the c‐axis of YBa2Cu3O7 is epitaxially aligned with the [001] direction of SrTiO3 irrespective of the misorientation. The {018} pole figure of YBa2Cu3O7 shows a fourfold symmetry which indicates that the films are ordered with respect to the substrate lattice. Moreover, the alignment in the {018} pole figure of the (220) reflections of SrTiO3 and the (018) reflections of YBa2Cu3O7 indicates that over the whole surface of the film the a‐ and b‐axes of YBa2Cu3O7 are aligned along the [100] and [010] direction of SrTiO3. The epitaxial nature of the films, the low density of particulates, and the lack of interdiffusion as concluded from secondary ion mass spectrometry measurements, allows for the preparation of heteroepitaxial stacks containing high‐...

Texture analysis of smooth in situ laser ablated YBa2Cu3O7 thin films on (100) SrTiO3

The texture of YBa2Cu3O7 thin films on (100) SrTiO3, grown by in situ laser ablation, was investigated by x‐ray diffraction. The surface morphology is smooth with only 105 cm−2 particulates of about 0.1 μm in diameter. High‐resolution x‐ray diffraction shows that the c‐axis of YBa2Cu3O7 is epitaxially aligned with the [001] direction of SrTiO3 irrespective of the misorientation. The {018} pole figure of YBa2Cu3O7 shows a fourfold symmetry which indicates that the films are ordered with respect to the substrate lattice. Moreover, the alignment in the {018} pole figure of the (220) reflections of SrTiO3 and the (018) reflections of YBa2Cu3O7 indicates that over the whole surface of the film the a‐ and b‐axes of YBa2Cu3O7 are aligned along the [100] and [010] direction of SrTiO3. The epitaxial nature of the films, the low density of particulates, and the lack of interdiffusion as concluded from secondary ion mass spectrometry measurements, allows for the preparation of heteroepitaxial stacks containing high‐...