Μm Wide Gap Research Articles

Conduction Conditions for Self-Healing of Metal Interconnect Using Copper Microparticles Dispersed with Silicone Oil

This study clarifies the conditions for the bridging and conduction of a gap on a metal interconnect using copper microparticles dispersed with silicon oil. An AC voltage applied to a metal interconnect with a gap covered by a dispersion of metal microparticles traps the metal microparticles in the gap owing to the influence of a dielectrophoretic force on the interconnect, thus forming a metal microparticle chain. The current was tuned independently of the applied voltage by changing the external resistance. An AC voltage of 32 kHz was applied to a 10 µm wide gap on a metal interconnect covered with 3 µm diameter copper microparticles dispersed with silicone oil. Consequently, the copper microparticle chains physically bridged the interconnect and exhibited electrical conductivity at an applied voltage of 14 Vrms or higher and a post-bridging current of 350 mArms or lower. It was shown that the copper microparticle chains did not exhibit electrical conductivity at low applied voltages, even if the microparticle chains bridged the gap. A voltage higher than a certain value was required to achieve electrical conductivity, whereas an excessive voltage caused bubble formation and destroyed the bridges. These phenomena were explained based on the applied voltage and reference value of the current after bridging.

Integrity and wound healing of rainbow trout intestinal epithelial cell sheets at hypo-, normo-, and hyper-thermic temperatures

How temperature influences fish physiological systems, such as the intestinal barrier, is important for understanding and alleviating the impact of global warming on fish and aquaculture. Monolayers of the rainbow trout cell line, RTgutGC, with or without linear 500μm wide gaps (wounds) were the in vitro models used to study the integrity and healing of intestinal epithelial sheets at different temperatures. Cultures at hypothermic (4°C) or hyperthermic (≥ 26°C) temperatures were compared to normothermic control cultures (18-22°C). Monolayers remained intact for at least a week at temperatures from 4 to 28°C, but had lost their integrity after 3h at 32°C as the cells pulled away from one another and from the plastic surface. F-actin appeared as prominent stress fibers in cells at 28°C and as blobs in cells at 32°C. At normothermia and at 26°C, cells migrated as sheets into the gaps and closed (healed) the gaps within 5-6 days. By contrast, wounds took 14 days to heal at 4°C. At 28°C some cells migrated into the gap in the first few days but mainly as single cells rather than collectively and wounds never healed. When monolayers with wounds were challenged at 32°C for 3h and returned to 18-22°C, cells lost their shape and actin organization and over the next 6 days detached and died. When monolayers were subjected to 26°C for 24h and challenged at 32°C for 3h prior to being placed at 18-22°C, cell shape and actin cytoskeleton were maintained, and wounds were healed over 6 days. Thus, intestinal epithelial cells become thermostabilized for shape, cytoskeleton and migration by a prior heat exposure.

Unconventional domain wall magnetoresistance of patterned Ni/Nb bilayer structures below superconducting transition temperature of Nb

Scattering of spin-up and spin-down electrons while passing through a ferromagnetic domain wall (DW) leads to an additional resistance for transport current, usually observed prominently in constricted magnetic structures. In this report we use the resistance of the DW as a probe to find an indirect signatures of the theoretically predicted spin-singlet supercurrent to spin-triplet supercurrent conversion effect of ferromagnetic DWs. Here we examine the DW induced resistance in Ni stripe in a bilayer Ni/Nb geometry in the normal state and in the superconducting state of Nb. By making a 3 μm wide gap in the top Nb layer we routed the transport current through the Ni layer in the normal state and in the superconducting state of Nb. In the normal state of Nb, in-field transport measurements showed a clear domain wall magneto-resistance (DWMR) peak of amplitude ∼5.9 mΩ near the coercive field, where the DW density is expected to be maximum. Interestingly, however, below the superconducting transition temperature of Nb, the DWMR peak of the Ni layer showed a sharp drop in the field range where the number of DWs become maximum. This observation may be a possible signature of magnetic DW induced spin-triplet correlations in the Ni layer due to the direct injection of spin-singlet Cooper pairs from Nb into the magnetic DWs.

Intra-cavity dynamics in a microplasma channel by side-on imaging

Here, a microplasma channel was investigated. The design was developed from a recently presented modular microplasma array. The setup consists of three stacked layers: a magnet, a dielectric foil and two nickel foils that are separated by a 120 μm wide gap. The magnet is grounded while the two nickel foils are powered. The channel is in two dimensions identical (50 μm high and 120 μm wide) to a single cavity of the microplasma arrays while it is two orders of magnitude longer. Unlike the microplasma arrays, the channel provides an additional optical access to the inside of the cavity from the side. The setup was operated with a triangular voltage with a frequency of 10 kHz and an amplitude of up to 700 V at atmospheric pressure. Phase resolved emission images were used to investigate the microplasma channel dynamics with line of sight from the top and from the side to the inside of the cavity. The top view images revealed that the discharge in the microplasma channel and the microplasma arrays behave similar. The already known asymmetric discharge behavior, the self-pulsing and the wavelike ignition was also observed in the microplasma channel. For the wavelike ignition in the channel a simple one dimensional model was proposed. With the additional side view images the asymmetric discharge behavior was examined more thoroughly. Unlike in the microplasma arrays, the discharge expands here in both half periods of the applied voltage above the upper edge of the powered electrodes. The discharge extends over a larger width in the half period, in which the potential of the upper electrodes is increasing, while it extends over a larger height in the other half period. Phase resolved images were also used to investigate the ignition phase of the discharge. The discharge ignites in the two half periods on a different height. This was explained by modeling the drift and diffusion of the charged particles between two discharge pulses. The new insights into the discharge dynamics in the microplasma channel will help to understand the behavior of the discharge in the microplasma arrays.

Spatio-temporal control of neuronal network formation with micropatterned thermoresponsive cell culture substrates

Spatio-temporal control of neuronal network formation with micropatterned thermoresponsive cell culture substrates

Voltage and current conditions for nanoparticle chain formation using dielectrophoresis

Here, the voltage and current conditions required to form a nanoparticle chain bridging a gap between electrodes that is several tens of micrometres wide have been examined. When a voltage is applied to a gap between electrodes covered with a dispersion of nanoparticles, the nanoparticles are trapped in the gap by dielectrophoresis, forming a nanoparticle chain. It has been considered that a nanoparticle chain is formed in a gap only when a voltage higher than a certain value with a current lower than a certain value is applied to the gap. In this work, certain voltages were first applied with changing current to a 10 μm-wide gap between electrodes covered with a dispersion of 150 nm-diameter gold nanoparticles, and they found that a nanoparticle chain was formed only when 6.1 V rms or more with 15 mA rms or less was applied. Next, the process of nanoparticle chain formation in a 10 μm-wide gap was directly observed with high-magnification and high-speed microscopy, and they clarified the behaviour of nanoparticle chain formation when a low voltage, high voltage with high current, and high voltage with low current were applied. Finally, they measured the critical value of current for nanoparticle chain formation in a gap several tens of micrometres wide.

Electromigration in sintered nanoporous copper

The current feed capacity of electrical interconnects is mainly limited by the poor electromigration (EM) resistance of lead free-solder interconnects. Thus, the community investigates alternative interconnect approaches and materials, e.g. all-copper interconnects using copper pastes. EM is an electron scattering based transport of metal atoms, occurring at high current densities, resulting in voids and thus finally leads to an open interconnect. For all-copper interconnects, it is expected that the maximum current density could be increased, while power losses can be mitigated, due to the higher EM resistance and reduced resistivity of copper compared to solder, respectively. However, all-copper interconnects formed by copper pastes applied without pressure result in a porous copper interconnect morphology with unknown EM performance. Thus, the authors report on results of EM tests on nanoporous copper films. The investigated copper paste is especially designed to be used for flip chip interconnects and contains nano and micron sized copper particles. Paste films were performed by doctor blading, followed by a sintering process at 200°C in formic acid. SEM analysis on FIB cross-sections of sintered films revealed the fusion of the nanoparticles to a nanoporous, sponge like morphology with embedded microparticles. Furthermore, a porosity of approximately 30% could be identified. The high porosity results in a non deterministic electrical network with a measured effective resistivity of ~10 μΩ cm, which is five times higher than the one of bulk copper (1.78 μΩ cm). For detailed investigations of the EM characteristics a setup, as well as a specific test sample layout were designed and implemented. The setup is capable to feed a current of up to 40 A to eight serial samples in a temperature range from room temperature to 250°C in ambient atmosphere. The test samples consist of copper lines, relief printed onto a silicon based carrier substrate, to bridge a 200 μm wide gap between two electrochemically deposited copper electrodes. The voltage drop across the copper line can be measured while driving the current through the line, by four point probing. In addition, a platinum based thermocouple (PT1000) is implemented on the carrier substrate beneath the nanoporous copper. It allows to prove the temperature of the nanoporous copper, to derive exact test conditions and the temperature coefficient of resistance of the nanoporous copper. Initial tests of samples exposed to elevated temperatures above 90°C, but without any current applied, resulted in the resistance increase of the nanoporous copper due to oxidation. Accordingly, a photoresist coverage was applied on the copper lines to mitigate the copper oxidation to levels acceptable for EM testing. A series of EM tests were then performed under constant current conditions to derive the EM kinetics and to explore the damage mechanisms. At current densities of 1 MA/cm^2 and a sample temperature of 90°C, the observed ‘time to failure’ of the nanoporous copper was more than six times higher than the one of tin based lead free solder. Furthermore, the authors will summarize their findings of the EM study performed on the nanoporous copper.

Fast and uniform growth of graphene glass using confined-flow chemical vapor deposition and its unique applications

Fast and uniform growth of high-quality graphene on conventional glass is of great importance for practical applications of graphene glass. We report herein a confined-flow chemical vapor deposition (CVD) approach for the high-efficiency fabrication of graphene glass. The key feature of our approach is the fabrication of a 2–4 μm wide gap above the glass substrate, with plenty of stumbling blocks; this gap was found to significantly increase the collision probability of the carbon precursors and reactive fragments between one another and with the glass surface. As a result, the growth rate of graphene glass increased remarkably, together with an improvement in the growth quality and uniformity as compared to those in the conventional gas flow CVD technique. These high-quality graphene glasses exhibited an excellent defogging performance with much higher defogging speed and higher stability compared to those previously reported. The graphene sapphire glass was found to be an ideal substrate for growing uniform and ultra-smooth aluminum nitride thin films without the tedious pre-deposition of a buffer layer. The presented confined-flow CVD approach offers a simple and low-cost route for the mass production of graphene glass, which is believed to promote the practical applications of various graphene glasses.

An Innovative Cell Microincubator for Drug Discovery Based on 3D Silicon Structures

We recently employed three-dimensional (3D) silicon microstructures (SMSs) consisting in arrays of 3 μm-thick silicon walls separated by 50 μm-deep, 5 μm-wide gaps, as microincubators for monitoring the biomechanical properties of tumor cells. They were here applied to investigate the in vitro behavior of HT1080 human fibrosarcoma cells driven to apoptosis by the chemotherapeutic drug Bleomycin. Our results, obtained by fluorescence microscopy, demonstrated that HT1080 cells exhibited a great ability to colonize the narrow gaps. Remarkably, HT1080 cells grown on 3D-SMS, when treated with the DNA damaging agent Bleomycin under conditions leading to apoptosis, tended to shrink, reducing their volume and mimicking the normal behavior of apoptotic cells, and were prone to leave the gaps. Finally, we performed label-free detection of cells adherent to the vertical silicon wall, inside the gap of 3D-SMS, by exploiting optical low coherence reflectometry using infrared, low power radiation. This kind of approach may become a new tool for increasing automation in the drug discovery area. Our results open new perspectives in view of future applications of the 3D-SMS as the core element of a lab-on-a-chip suitable for screening the effect of new molecules potentially able to kill tumor cells.

Atrial Excitation-Contraction Coupling and Ca Wave Propagation in Normal and Failing Hearts

We compared excitation-contraction coupling and Ca wave propagation in normal and heart failure (HF) rabbit atrial myocytes. Cytosolic Ca transients (Fluo-4 or Rhod-2), sarcoplasmic reticulum (SR) [Ca] (Fluo-5N) and mitochondrial localization (Mitotracker Red) were recorded by confocal microscopy. SEA and Ru360 were used to inhibit sarcolemmal Na/Ca exchange (NCX) or mitochondrial Ca uptake, respectively. In normal and HF rabbit atrial myocytes transverse tubules are missing, and the peripheral junctional SR (j-SR) is separated from the central non-junctional SR (nj-SR) by a 1-2 µm wide gap that is largely devoid of mitochondria and SR structures. During action potential (AP) stimulation SR Ca release initiated from the j-SR and propagated in centripetal direction via Ca-induced Ca release (CICR) from nj-SR. The centripetal Ca propagation velocity was highest across the gap between j-SR and nj-SR, slowed during propagation across the nj-SR and increased after Ru360 application. In HF, the centripetal propagation velocity was higher and mitochondrial density was decreased. Spontaneous Ca waves propagated with a leading wave front located to the cell periphery, i.e. arising from j-SR Ca release. Nearly half of all Ca waves in normal cells, but <10% in normal cells pretreated with SEA and none in ventricular cells triggered an AP, followed by a whole-cell Ca transient (termed here 'arrhythmogenic Ca waves'). The incidence of spontaneous Ca waves, the fraction of arrhythmogenic Ca waves and NCX activity were significantly increased in HF. In summary, the lack of mitochondria in the gap between j-SR and nj-SR enables rapid propagation of CICR from the j-SR to the nj-SR. Decreased mitochondrial Ca uptake in HF contributes to an increased centripetal Ca propagation velocity. Atrial myocytes are prone to develop NCX-dependent arrhythmogenic Ca waves, which is further accentuated in HF.

Structural and Functional Arrangements of Atrial Myocytes that Facilitate Excitation-Contraction Coupling

Rabbit atrial myocytes lack transverse tubules and only the peripheral sarcoplasmic reticulum (SR) is in contact with the surface membrane (junctional SR; j-SR) and exposed to Ca influx through voltage-gated sarcolemmal Ca channels that initiates Ca release which propagates centripetally by Ca-induced Ca release from non-junctional SR (nj-SR). In this study we examined the structural and functional characteristics of excitation-contraction coupling (ECC) unique to atrial myocytes. Subsarcolemmal (SS) Ca release from j-SR preceded release at central (CT) nj-SR regions, and SS release was of higher amplitude compared to CT release. Using simultaneous measurements of cytosolic ([Ca]i) and intra-SR ([Ca]SR) Ca, we show that depletions of SS [Ca]SR were smaller compared to CT [Ca]SR depletions during electrical stimulation. Atrial myocytes revealed an approximately 1-2 µm wide gap devoid of mitochondria and SR structures between the j-SR and the nj-SR that the Ca signal must traverse to activate release from nj-SR. The spread of Ca from the j-SR to the nj-SR occurred very rapidly and was aided by the absence of mitochondria which might buffer the diffusion of Ca. In contrast to SS release, the continuation of Ca release through the nj-SR to the cell center occurred much slower in a Ca wave-like fashion, and the rise of [Ca]i detected at individual release sites of the nj-SR preceded the depletion of [Ca]SR. During this latency period a transient elevation of [Ca]SR was observed that acted as an intra-SR Ca sensitization wave that may facilitate the spread of excitation through the nj-SR via the luminal Ca-sensitivity of the ryanodine receptor Ca release channel. In summary, we have identified key structural and functional characteristics of atrial myocytes that allow for efficient ECC in the intact heart.

A new cell-selective three-dimensional microincubator based on silicon photonic crystals.

In this work, we show that vertical, high aspect-ratio (HAR) photonic crystals (PhCs), consisting of periodic arrays of 5 µm wide gaps with depth of 50 µm separated by 3 µm thick silicon walls, fabricated by electrochemical micromachining, can be used as three-dimensional microincubators, allowing cell lines to be selectively grown into the gaps. Silicon micromachined dice incorporating regions with different surface profiles, namely flat silicon and deeply etched PhC, were used as microincubators for culturing adherent cell lines with different morphology and adhesion properties. We extensively investigated and compared the proliferative behavior on HAR PhCs of eight human cell models, with different origins, such as the epithelial (SW613-B3; HeLa; SW480; HCT116; HT29) and the mesenchymal (MRC-5V1; CF; HT1080). We also verified the contribution of cell sedimentation into the silicon gaps. Fluorescence microscopy analysis highlights that only cell lines that exhibit, in the tested culture condition, the behavior typical of the mesenchymal phenotype are able to penetrate into the gaps of the PhC, extending their body deeply in the narrow gaps between adjacent silicon walls, and to grow adherent to the vertical surfaces of silicon. Results reported in this work, confirmed in various experiments, strongly support our statement that such three-dimensional microstructures have selection capabilities with regard to the cell lines that can actively populate the narrow gaps. Cells with a mesenchymal phenotype could be exploited in the next future as bioreceptors, in combination with HAR PhC optical transducers, e.g., for label-free optical detection of cellular activities involving changes in cell adhesion and/or morphology (e.g., apoptosis) in a three-dimensional microenvironment.

Silicon sub-micron-gap deep trench Pirani vacuum gauge for operation at atmospheric pressure

The operation of a bulk micromachined Pirani vacuum gauge at atmospheric pressure is demonstrated. The device is fabricated on a silicon-on-insulator (SOI) wafer with a 5 µm thick device layer by using a one-mask, deep etching process. The 250 nm wide vertical gap fabricated by the deep etching of silicon has made operation at atmospheric pressure possible. The pressure range dependence on the change in the length of the heater and the length of the gap is discussed. Further, the performance dependence on different gaps is measured using 1.5 µm and 5.5 µm wide gaps. Measurement from 4 to 101 300 Pa is performed, and high sensitivity from 1000 to 101 300 Pa is confirmed.

Performance of a new LMRPC prototype for the STAR MTD system

A new prototype of a Long-Strip Multi-Gap Resistive Plate Chamber (LMRPC) for the STAR Muon Telescope Detector (MTD) at RHIC has been developed. This prototype has an active area of 52×90 cm 2 and consists of six 250 μm wide gaps. Each detector has 12 strips, read-out at both ends, which are each 3.8 cm wide and 90 cm long with 0.6 cm intervals. In cosmic-ray tests, the efficiency was larger than 95% and the time resolution was ∼75 ps for the 94% Freon, 5% iso-butane, and 1% SF 6 gas mixture. There was good uniformity in the performance across the different strips. The module was also tested in a proton beam at IHEP in Beijing. The efficiency was close to 100% and the best timing resolution achieved was 55 ps for the 90% Freon, 5% iso-butane, and 5% SF 6 gas mixture. Trigger scans along and across the strip direction were also performed.

Gentamicin release from commercially-available gentamicin-loaded PMMA bone cements in a prosthesis-related interfacial gap model and their antibacterial efficacy

BackgroundAround about 1970, a gentamicin-loaded poly (methylmethacrylate) (PMMA) bone cement brand (Refobacin Palacos R) was introduced to control infection in joint arthroplasties. In 2005, this brand was replaced by two gentamicin-loaded follow-up brands, Refobacin Bone Cement R and Palacos R + G. In addition, another gentamicin-loaded cement brand, SmartSet GHV, was introduced in Europe in 2003. In the present study, we investigated differences in gentamicin release and the antibacterial efficacy of the eluent between these four cement brands.Methods200 μm-wide gaps were made in samples of each cement and filled with buffer in order to measure the gentamicin release. Release kinetics were related to bone cement powder particle characteristics and wettabilities of the cement surfaces. Gaps were also inoculated with bacteria isolated from infected prostheses for 24 h and their survival determined. Gentamicin release and bacterial survival were statistically analysed using the Student's t-test.ResultsAll three Palacos variants showed equal burst releases but each of the successor Palacos cements showed significantly higher sustained releases. SmartSet GHV showed a significantly higher burst release, while its sustained release was comparable with original Palacos. A gentamicin-sensitive bacterium did not survive in the high gentamicin concentrations in the interfacial gaps, while a gentamicin-resistant strain did, regardless of the type of cement used. Survival was independent of the level of burst release by the bone cement.ConclusionsAlthough marketed as the original gentamicin-loaded Palacos cement, orthopaedic surgeons should be aware that the successor cements do not appear to have the same release characteristics as the original one. Overall, high gentamicin concentrations were reached inside our prosthesis-related interfacial gap model. These concentrations may be expected to effectively decontaminate the prosthesis-related interfacial gap directly after implantation, provided that these bacteria are sensitive for gentamicin.

Characterization of thermal cross-talk in a MEMS-based thermopile detector array

The spectral resolution of a MEMS-based IR microspectrometer critically depends on the thermal cross-talk between adjacent TE elements in the detector array. Thermal isolation between elements is realized by using bulk micromachining directly following CMOS processing. This paper reports on the characterization results of bridge-shaped TE detector elements that are cut out of a membrane. Elements with dimensions of 650 × 36 µm2 are separated by 10 µm wide gaps in order to minimize the thermal cross-talk by heat conduction through the support structure. The static and dynamic aspects of thermal cross-talk have been evaluated with an emphasis on the effect of the thermal conductivity of air as a function of the package pressure.

Low-voltage electron emission from thin [Pb(Mg1/3Nb2/3)O3]0.72 [PbTiO3]0.28 single crystals induced by ferroelectric polarization switching

Electron emission from [Pb(Mg1/3Nb2/3)O3]0.72 [PbTiO3]0.28 (PMN–PT) thin ferroelectric single crystals is reported at ultralow voltages down to 20 V per 400 μm thickness, and for up to 109 switching cycles. The PMN–PT samples were prepared with split gold top electrodes exhibiting a 25 μm wide gap region. Applying a sinusoidal voltage between the two top electrodes and the bottom electrode initiated electron emission from the gap region. The emitted electrons were collected under UHV conditions using two single electron counters arranged under an angle of 90°. Two emission regimes have been identified. Both are attributable to weak electron emission, however, clearly separated by the onset of complete ferroelectric polarization switching. This is also confirmed by recording nanoscale ferroelectric hysteresis loops by means of piezoresponse force microscopy. The emitted electrons are found to have a broad energy distribution with the maximum kinetic energies reaching 110 and 50 eV for applied switching voltages of 140 and 110 V, respectively. Our results confirm that polarization reversal is the governing mechanism behind the electron-emission process in the thin PMN–PT samples. Also, the applied electric field strengths needed to trigger electron emission from the PMN–PT crystals are about 10 times lower compared to most other (ferroelectric) materials reported in the literature.

Field Electron Emission from Inkjet-Printed Carbon Black

We demonstrate the field electron emission from a carbon black dot array prepared by inkjet printing. A commercially available inkjet printer and drawing software were used to pattern the carbon-black-containing ink on the tungsten silicide surface which was deposited on a Si wafer. Field electron emission characteristics were measured using a diode configuration. It was found that oxygen reactive ion etching (RIE) of the printed carbon black is effective for obtaining the field emission. The turn-on voltage was 500 V and an emission current over 100 µA was obtained at a voltage of 1400 V with a 25 µm-wide gap between anode and cathode. It was also found that a rapid increase of the voltage is effective in increasing the emission current and the number of emission sites.

Ultrahigh frequency microplasmas from 1 pascal to 1 atmosphere

The generation of plasma-on-a-chip is examined for two extremes in gas pressure. The application of microplasmas as sensors of industrial vacuum processes requires stable operation at gas pressures of less than 1 Pa. In this low-pressure regime, the addition of a static magnetic field that causes electron cyclotron resonance is shown to increase the emission intensity of the microplasma by 50%. Using atomic emission spectrometry, the detection of helium in air is found to have a detection limit of 1000 ppm, which is three orders of magnitude worse than the DL of SO2 in argon. The loss of sensitivity is traced to the high excitation energy threshold of He, and to the poor ionization efficiency inherent in an air plasma. At atmospheric pressure (105 Pa), a microdischarge is described that operates in a 25 µm-wide gap in a microstrip transmission line resonator operating at 900 MHz. The volume of the discharge is ∼10−7 cm3, and this allows an atmospheric air discharge to be initiated and sustained using less than 3 W of power.

Effects of ozone assisted deposition on the dielectric properties of 90° off-axis radio frequency magnetron sputtered SrTiO3

The low and high frequency dielectric properties of epitaxial SrTiO3 (STO) thin films deposited on LaAlO3 are presented. The effects of in situ ozone annealing during the early stages of deposition were explored. X-ray diffraction results indicated that the ozone treatment resulted in more symmetric and sharper diffraction peaks. In addition, the peaks for the ozone treated samples were shifted in 2θ towards values approaching the bulk. The dielectric constant of the ozone treated samples increased from 275 at room temperature to 1175 at 22 K (measured at 100 kHz). The effective loss tangent of the device remained between 1×10−4 and 1×10−3 down to 100 K, where it began to increase. These properties were far superior to those films deposited without ozone. For high frequency measurements, coplanar waveguide structures with a centerline width of 20 and 40 μm wide gaps were patterned into YBa2Cu3O7 films deposited on top of the 0.5 μm thick STO. For the ozone treated films, Q values of up to 70% greater were achieved at 4 GHz and 75 K with little effect on the frequency modulation (compared to films deposited without ozone).