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A number of quantum technologies require macroscopic mechanical oscillators possessing ultra-high motional Q-factors. These can be used to explore the macroscopic limits of quantum mechanics, to develop quantum sensors and to test the quantum nature of gravity. One approach is to trap nanometer to micron-sized particles in 3D; however, the use of ion or optical traps suffers from a number of difficulties including electrodynamic noise due to patch fields, damage to the particles due to unwanted laser heating, or difficulty in reaching low pressures due to particle loss. In this work, we report a completely passive, magnetic trap which confines a micro-diamond in 3D and which requires no active power—optical or electrical. We design, model, fabricate, and test the operation of our magneto-mechanical trap and experimentally demonstrate trapping down to ∼0.1 Torr. We measure the position fluctuation of the trapped micro-diamond as a function of pressure and find good agreement with Brownian theory.

Using an atomic force microscope (AFM) modified to perform piezo-AFM we have investigated the piezoelectric response of sol-gel thin film lead zirconate titanate (PZT 30/70, PbZr0.3Ti0.7O3) on Pt-Ti/SiO2/Si to a quasi-dc electric field. By applying a sinusoidal 2 Hz ac waveform between the AFM cantilever and ground we have generated strain field, or butterfly loops for the PZT film. Coercive fields for the thin films have been calculated from the minimum point of the strain before reversal for the system and are shown to be −30 and +32 V/μm in absolute terms and −23 and +39 V/μm in terms relative to the charge trapped at the electrode interface. The maximum strain of the system was shown at applied biases of ±10 V and was 0.3% at a bias of +10 V, although at this bias the sample was not showing saturated behavior. By relating the offset of the butterfly loops to the charge density generated by defects at the PZT–electrode interface, calculated to be 0.025 Cm−2, an estimate of the number of defects at the ...

Tobacco mosaic virus (TMV) particles have been assembled at predetermined locations on the surface of a ferroelectric thin film with the composition PbZr0.3Ti0.7O3. The domain structure, hence the surface depolarization field for the ferroelectric associated with the bending of the ferroelectric band structure, was modified at length scales of around 2μm. A suspension of TMV particles was deposited onto the surface of the ferroelectric over the region where domain modification had been performed. SPM images (intermittent contact) revealed that the virus particles were attracted to regions of the surface that had either been positively modified or were nominally neutral. Regions of modified negative surface charge effectively repelled the virus particles.

A zinc oxide (ZnO) nanorod array exhibiting an intense deep-level emission (DLE) was probed at the Zn K edge (9659 eV) using extended x-ray absorption fine structure (EXAFS) analysis. X-ray excited optical luminescence was used to obtain site-specific information around the absorbing Zn atom using optically detected EXAFS (ODXAS). The visible-emission corresponds to defects in ZnO crystal lattice introduced during growth. A comparative study between red (660 nm) and green (500 nm) DLE was conducted by collecting specific wavelength emissions of the optically detected x-ray absorption spectra. It was shown that red emission primarily originates from the nanorod surface, and green emission was linked to disorder occurring on Zn sites. We show that ODXAS can distinguish between two emission regions and provides a platform to link defect emission with specific crystal structures.

ZnO nanorods synthesised using an aqueous pH 11 solution are shown to exhibit surface-sensitive morphology post-annealing in oxygen, air, and nitrogen as shown by scanning electron microscopy and transmission electron microscopy analysis. Raman analysis confirms the nanorods were nitrogen-doped and that nitrogen incorporation takes place during the synthesis procedure in the form of N-Hx. A strong green photoluminescence is observed post-annealing for all samples, the intensity of which is dependent on the atmosphere of anneal. This luminescence is linked to zinc vacancies as recent reports have indicated that these defects are energetically favoured with the annealing conditions used herein. ZnO-nanorod/CuSCN diodes are fabricated to examine the effect of material properties on photodetector device performance. The devices exhibit a photocurrent at zero bias, creating a self-powered photodetector. A photocurrent response of 30 μA (at 6 mW cm−2 irradiance) is measured, with a rise time of ∼25 ns, and sensitivity to both UV and visible light (475–525 nm).

Asymmetrical electrical boundary conditions in (001)-oriented Pb(Zr0.2TiO0.8)O3 (PZT) epitaxial ultrathin ferroelectric films are exploited to control surface photochemical reactivity determined by the sign of the surface polarization charge. It is shown that the preferential orientation of polarization in the as-grown PZT layer can be manipulated by choosing an appropriate type of bottom electrode material. PZT films deposited on the SrRuO3 electrodes exhibit preferential upward polarization (C+) whilst the same films grown on the (La,Sr)CoO3-electrodes are polarized downward (C−). Photochemical activity of the PZT surfaces with different surface polarization charges has been tested by studying deposition of silver nanoparticles from AgNO3 solution under UV irradiation. PZT surfaces with preferential C+ orientation possess a more active surface for metal reduction than their C− counterparts, evidenced by large differences in the concentration of deposited silver nanoparticles. This effect is attributed to band bending at the bottom interface which varies depending on the difference in work functions of PZT and electrode materials.

We used controlled bending of a ZnO/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) diode at known strain rates to measure the mechanical-to-electrical energy conversion efficiency. The mechanical energy input into the nanostructured diode was measured as 330 ± 2 nJ cm−2. The electrical energy output was calculated by integrating the product of the short-circuit current and open-circuit voltage over time. This gives a measured external efficiency of the device at a bending rate of 500 mm/min of 0.0067%. The efficiency increased exponentially with bending rate, though this increase must slow as the mechanical coupling efficiency is approached, which gives a maximum possible efficiency of 23% for ZnO.

We have investigated a technique that is a combination of sputtering, evaporation, and annealing for the production of thin film and nanostructured PbTiO3 that we show to be piezoelectric via piezoresponse force microscopy (PFM). The synthesis technique involved depositing lead, via thermal evaporation, onto the surface of a variety of substrates that had Ti as the uppermost layer, followed by conventional or rapid thermal annealing in air to form PbTiO3. By careful control of the deposition time, samples ranging from discrete nanoislands to thin films could be produced. The nanoisland samples while exhibiting a piezoelectric response displayed little or no domain structure even with grains as large as 100 nm in diameter. However, we see a domain pattern in the thin film samples. We show that there are difficulties in poling PbTiO3 thin films using PFM due to the high coercive field required and the number of shorts through the thin films.

Thiol-capped CdTe nanocrystals were used to fabricate light-emitting diodes, consisting of an emissive nanocrystal multilayer deposited via layer-by-layer, sandwiched between indium-tin-oxide and aluminum electrodes. The emissive and electrical properties of devices with different numbers of nanocrystal layers were studied. The improved structural homogeneity of the nanocrystal multilayer allowed for stable and repeatable current- and electroluminescence-voltage characteristics. These indicate that both current and electroluminescence are electric-field dependent. Devices were operated under ambient conditions and a clear red-light was detected. The best-performing device shows a peak external efficiency of 0.51% and was measured at 0.35mA/cm2 and 3.3V.