Enhanced Corrosion Resistance in Aluminum-Based Electrolyzer Components via Stoichiometry Tuned Atomic Layer-Deposited TiOx Films.

Titanium (Ti) is widely used as anode current collectors in proton exchange membrane (PEM)-based water electrolyzers due to its self-passivated oxide layer, which protects it from corrosion in acidic solutions. However, the cost of the material and machining process for Ti is high. A wider utilization of water electrolyzers to produce hydrogen could be favored by the use of less expensive coated aluminum (Al) substrates, which could potentially replace high-cost Ti-based components. It is shown here by depositing a pinhole-free oxygen vacancy-rich titanium oxide (TiOx) protection layer by atomic layer deposition (ALD), the corrosion resistance of Al substrates in acidic environments at oxygen evolution potentials can be enhanced. The optimization of the oxygen vacancy concentration is accomplished by tuning the ALD parameters to achieve ideal stoichiometry and conformal coating on rough substrates. The robustness of the coatings was evaluated at high potentials (2.4 V vs NHE = normal hydrogen electrode) in low pH conditions. A low TiOx dissolution rate of the order of ∼6 nm year-1 was observed. By testing under industrially relevant conditions, i.e., high applied voltages (2.4 V) and low pH, an Al loss at around the zero ppb level was achieved using optimized ALD parameters. It is proposed that a 40 nm TiOx coating on Al may be adequate to provide 60,000 h of durability in a PEM water electrolyzer anode current collector.

Achieving a High Thermally Conductive One Micron AlN Deposition by High Power Impulse Magnetron Sputtering plus Kick.

High-power impulse magnetron sputtering (HiPIMS) plus kick is a physical vapor deposition method that employs bipolar microsecond-scale voltage pulsing to precisely control the ion energy during sputter deposition. HiPIMS plus kick for AlN deposition is difficult since nitride deposition is challenged by low surface diffusion and high susceptibility to ion damage. In this current study, a systematic examination of the process parameters of HiPIMS plus kick was conducted. Under optimized main negative pulsing conditions, this study documented that a 25 V positive kick biasing for AlN deposition is ideal for optimizing a high quality film, as shown by X-ray diffraction and transmission electron microscopy as well as optimal thermal conductivity while increasing high speed deposition (25 nm/min) and obtaining ultrasmooth surfaces (rms roughness = 0.5 nm). HiPIMS plus kick was employed to deposit a single-texture 1 µm AlN film with a 7.4° rocking curve, indicating well oriented grains, which correlated with high thermal conductivity (121 W/m·K). The data are consistent with the optimal kick voltage enabling enhanced surface diffusion due to ion-substrate collisions without damaging the AlN grains.

High Thermal Conductivity of Submicrometer Aluminum Nitride Thin Films Sputter-Deposited at Low Temperature.

Aluminum nitride (AlN) is one of the few electrically insulating materials with excellent thermal conductivity, but high-quality films typically require exceedingly hot deposition temperatures (>1000 °C). For thermal management applications in dense or high-power integrated circuits, it is important to deposit heat spreaders at low temperatures (<500 °C), without affecting the underlying electronics. Here, we demonstrate 100 nm to 1.7 µm thick AlN films achieved by low-temperature (<100 °C) sputtering, correlating their thermal properties with their grain size and interfacial quality, which we analyze by X-ray diffraction, transmission X-ray microscopy, as well as Raman and Auger spectroscopy. Controlling the deposition conditions through the partial pressure of reactive N2, we achieve an ∼3× variation in thermal conductivity (∼36-104 W m-1 K-1) of ∼600 nm films, with the upper range representing one of the highest values for such film thicknesses at room temperature, especially at deposition temperatures below 100 °C. Defect densities are also estimated from the thermal conductivity measurements, providing insight into the thermal engineering of AlN that can be optimized for application-specific heat spreading or thermal confinement.

A Local and Abscopal Effect Observed with Liposomal Encapsulation of Intratumorally Injected Oncolytic Adenoviral Therapy.

This study evaluated the in vivo therapeutic efficacy of oncolytic serotype 5 adenovirus TAV255 in CAR-deficient tumors. In vitro experiments were performed with cell lines that expressed different levels of CAR (HEK293, A549, CT26, 4T1, and MCF-7). Low CAR cells, such as CT26, were poorly transduced by Ad in vitro unless the adenovirus was encapsulated in liposomes. However, the CT26 tumor in an immune-competent mouse model responded to the unencapsulated TAV255; 33% of the tumors were induced into complete remission, and mice with complete remission rejected the rechallenge with cancer cell injection. Encapsulation of TAV255 improves its therapeutic efficacy by transducing more CT26 cells, as expected from in vitro results. In a bilateral tumor model, nonencapsulated TAV255 reduced the growth rate of the locally treated tumors but had no effect on the growth rate of the distant tumor site. Conversely, encapsulated TAV255-infected CT26 induced a delayed growth rate of both the primary injected tumor and the distant tumor, consistent with a robust immune response. In vivo, intratumorally injected unencapsulated adenoviruses infect CAR-negative cells with only limited efficiency. However, unencapsulated adenoviruses robustly inhibit the growth of CAR-deficient tumors, an effect that constitutes an 'in situ vaccination' by stimulating cytotoxic T cells.

Development of Adenovirus Containing Liposomes Produced by Extrusion vs. Homogenization: A Comparison for Scale-Up Purposes.

Adenovirus (Ad) is a widely studied viral vector for cancer therapy as it can be engineered to cause selective lysis of cancer cells. However, Ad delivery is limited in treating cancers that do not have coxsackievirus and adenovirus receptors (CAR). To overcome this challenge, Ad-encapsulated liposomes were developed that enhance the delivery of Ads and increase therapeutic efficacy. Cationic empty liposomes were manufactured first, to which an anionic Ad were added, which resulted in encapsulated Ad liposomes through charge interaction. Optimization of the liposome formula was carried out with series of formulation variables experiments using an extrusion process, which is ideal for laboratory-scale small batches. Later, the optimized formulation was manufactured with a homogenization technique-A high shear rotor-stator blending, that is ideal for large-scale manufacturing and is in compliance with Good Manufacturing Practices (GMP). Comparative in vitro transduction, physicochemical characterization, long-term storage stability at different temperature conditions, and in vivo animal studies were performed. Ad encapsulated liposomes transduced CAR deficient cells 100-fold more efficiently than the unencapsulated Ad (p ≤ 0.0001) in vitro, and 4-fold higher in tumors injected in nude mice in vivo. Both extrusion and homogenization performed similarly-with equivalent in vitro and in vivo transduction efficiencies, physicochemical characterization, and long-term storage stability. Thus, two Ad encapsulated liposomes preparation methods used herein, i.e., extrusion vs. homogenization were equivalent in terms of enhanced Ad performance and long-term storage stability; this will, hopefully, facilitate translation to the clinic.

Full Remission of CAR-Deficient Tumors by DOTAP-Folate Liposome Encapsulation of Adenovirus.

Adenovirus (Ad)-based vectors have shown considerable promise for gene therapy. However, Ad requires the coxsackievirus and adenovirus receptor (CAR) to enter cells efficiently and low CAR expression is found in many human cancers, which hinder adenoviral gene therapies. Here, cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)-folate liposomes (Df) encapsulating replication-deficient Ad were synthesized, which showed improved transfection efficiency in various CAR-deficient cell lines, including epithelial and hematopoietic cell types. When encapsulating replication-competent oncolytic Ad (TAV255) in DOTAP-folate liposome (TAV255-Df), the adenoviral structural protein, hexon, was readily produced in CAR-deficient cells, and the tumor cell killing ability was 5× higher than that of the non-encapsulated Ad. In CAR-deficient CT26 colon carcinoma murine models, replication-competent TAV255-Df treatment of subcutaneous tumors by intratumoral injection resulted in 67% full tumor remission, prolonged survival, and anti-cancer immunity when mice were rechallenged with cancer cells with no further treatment. The preclinical data shows that DOTAP-folate liposomes could significantly enhance the transfection efficiency of Ad in CAR-deficient cells and, therefore, could be a feasible strategy for applications in cancer treatment.

Remote Oxygen Scavenging of the Interfacial Oxide Layer in Ferroelectric Hafnium-Zirconium Oxide-Based Metal-Oxide-Semiconductor Structures.

Discovery of ferroelectricity in HfO2 has sparked a lot of interest in its use in memory and logic due to its CMOS compatibility and scalability. Devices that use ferroelectric HfO2 are being investigated; for example, the ferroelectric field-effect transistor (FEFET) is one of the leading candidates for next generation memory technology, due to its area, energy efficiency and fast operation. In an FEFET, a ferroelectric layer is deposited on Si, with an SiO2 layer of ∼1 nm thickness inevitably forming at the interface. This interfacial layer (IL) increases the gate voltage required to switch the polarization and write into the memory device, thereby increasing the energy required to operate FEFETs, and makes the technology incompatible with logic circuits. In this work, it is shown that a Pt/Ti/thin TiN gate electrode in a ferroelectric Hf0.5Zr0.5O2 based metal-oxide-semiconductor (MOS) structure can remotely scavenge oxygen from the IL, thinning it down to ∼0.5 nm. This IL reduction significantly reduces the ferroelectric polarization switching voltage with a ∼2× concomitant increase in the remnant polarization and a ∼3× increase in the abruptness of polarization switching consistent with density functional theory (DFT) calculations modeling the role of the IL layer in the gate stack electrostatics. The large increase in remnant polarization and abruptness of polarization switching are consistent with the oxygen diffusion in the scavenging process reducing oxygen vacancies in the HZO layer, thereby depinning the polarization of some of the HZO grains.

Tetravalent Doping in Fluorite-Based Ferroelectric Oxides for Reduced Voltage Operations.

First-principles calculations show a reduced energy barrier for polarization switching via a bulk phase transition by doping of hafnium-zirconium oxide (HZO). The tetragonal P42/nmc phase serves as a transition state for polarization switching of the polar orthorhombic Pca21 phase. Due to the high symmetry of the tetragonal phase, dopants can form more energetically favorable local oxygen bonding configurations in the tetragonal phase versus the orthorhombic phase. Significant bond strain is observed in the orthorhombic phase due to the low symmetry of the host crystal structure which decreases the relative stability of the doped orthorhombic phase compared to the doped tetragonal phase, thereby significantly lowering the barrier for switching but slightly affecting the polarization of the orthorhombic phase. Si is a promising dopant for an efficient ferroelectric device with minimal disturbance in the electronic structure parameters. Ge doping is suitable for stabilizing the tetragonal phase which shows a high k value.

Selective Pulsed Chemical Vapor Deposition of Water-Free TiO2/Al2O3 and HfO2/Al2O3 Nanolaminates on Si and SiO2 in Preference to SiCOH.

Highly selective and smooth TiO2/Al2O3 and HfO2/Al2O3 nanolaminates were deposited by water-free pulsed chemical vapor deposition (CVD) at 300 °C using titanium isopropoxide (Ti(OiPr)4) and hafnium tertbutoxide (Hf(OtBu)4) with trimethylaluminum (TMA). TMA was found to be the key factor for enhancing nucleation selectivity on SiO2 or Si versus SiCOH (hydrophobic, nonporous low k dielectric). With precise dosing of TMA, selective nucleation of TiO2/Al2O3 and HfO2/Al2O3 nanolaminates was achieved and smoother films were formed with higher selectivity compared to single precursor TiO2 and HfO2 CVD. The selectivity of TiO2/Al2O3 nanolaminate deposition increased from 34 to 44 (deposition on Si vs SiCOH), while RMS roughness of the film of Si decreased from 2.8 to 0.38 nm. The selectivity of HfO2/Al2O3 deposition increased from 14 to 73, while the RMS roughness of HfO2/Al2O3 on Si was maintained at a similar value of 0.78 nm. Deposition of water-free pulsed CVD TiO2/Al2O3 and HfO2/Al2O3 nanolaminates was conducted on a Cu/SiCOH patterned sample to study their nanoselectivity. Transmission electron microscopy images of the Cu/SiCOH patterned sample demonstrated that highly selective and smooth TiO2/Al2O3 and HfO2/Al2O3 nanolaminates can be formed on a nanoscale pattern.

Sub-Nanometer Interfacial Oxides on Highly Oriented Pyrolytic Graphite and Carbon Nanotubes Enabled by Lateral Oxide Growth.

A new generation of compact and high-speed electronic devices, based on carbon, would be enabled through the development of robust gate oxides with sub-nanometer effective oxide thickness (EOT) on carbon nanotubes or graphene nanoribbons. However, to date, the lack of dangling bonds on sp2 oriented graphene sheets has limited the high precursor nucleation density enabling atomic layer deposition of sub-1 nm EOT gate oxides. It is shown here that by deploying a low-temperature AlOx (LT AlOx) process, involving atomic layer deposition (ALD) of Al2O3 at 50 °C with a chemical vapor deposition (CVD) component, a high nucleation density layer can be formed, which templates the growth of a high-k dielectric, such as HfO2. Atomic force microscopy (AFM) imaging shows that at 50 °C, the Al2O3 spontaneously forms a pinhole-free, sub-2 nm layer on graphene. Density functional theory (DFT) based simulations indicate that the spreading out of AlOx clusters on the carbon surface enables conformal oxide deposition. Device applications of the LT AlOx deposition scheme were investigated through electrical measurements on metal oxide semiconductor capacitors (MOSCAPs) with Al2O3/HfO2 bilayer gate oxides using both standard Ti/Pt metal gates as well as TiN/Ti/Pd gettering gates. In this study, LT AlOx was used to nucleate HfO2 and it was shown that bilayer gate oxide stacks of 2.85 and 3.15 nm were able to achieve continuous coverage on carbon nanotubes (CNTs). The robustness of the bilayer was tested through deployment in a CNT-based field-effect transistor (FET) configuration with a gate leakage of less than 10-8 A/µm per CNT.

Hafnium-zirconium oxide interface models with a semiconductor and metal for ferroelectric devices.

Density functional theory (DFT) is employed to investigate ferroelectric (FE) hafnium-zirconium oxide stack models for both metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures. The role of dielectric (DE) interlayers at the ferroelectric interfaces with metals and semiconductors and the effects of thickness scaling of FE and DE layers were investigated using atomic stack models. A high internal field is induced in the FE and DE layers by the FE polarization field which can promote defect generation leading to limited endurance. It is also shown that device operation will be adversely affected by too thick DE interlayers due to high operating voltage. These DFT models elucidate the underlying mechanisms of the lower endurance in experimental MIS devices compared to MIM devices and provide insights into the fundamental mechanisms at the interfaces.

Correction: Hafnium-zirconium oxide interface models with a semiconductor and metal for ferroelectric devices.

[This corrects the article DOI: 10.1039/D1NA00230A.].

Immunostimulatory TLR7 agonist-nanoparticles together with checkpoint blockade for effective cancer immunotherapy.

Mono- or dual-checkpoint inhibitors for immunotherapy have changed the paradigm of cancer care; however, only a minority of patients responds to such treatment. Combining small molecule immuno-stimulators can improve treatment efficacy, but they are restricted by poor pharmacokinetics. In this study, TLR7 agonists conjugated onto silica nanoparticles showed extended drug localization after intratumoral injection. The nanoparticle-based TLR7 agonist increased immune stimulation by activating the TLR7 signaling pathway. When treating CT26 colon cancer, nanoparticle conjugated TLR7 agonists increased T cell infiltration into the tumors by > 4× and upregulated expression of the interferon γ gene compared to its unconjugated counterpart by ~2×. Toxicity assays established that the conjugated TLR7 agonist is a safe agent at the effective dose. When combined with checkpoint inhibitors that target programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), a 10-100× increase in immune cell migration was observed; furthermore, 100 mm3 tumors were treated and a 60% remission rate was observed including remission at contralateral non-injected tumors. The data show that nanoparticle based TLR7 agonists are safe and can potentiate the effectiveness of checkpoint inhibitors in immunotherapy resistant tumor models and promote a long-term specific memory immune function.

Understanding the Mechanism of Electronic Defect Suppression Enabled by Nonidealities in Atomic Layer Deposition.

Silicon germanium (SiGe) is a multifunctional material considered for quantum computing, neuromorphic devices, and CMOS transistors. However, implementation of SiGe in nanoscale electronic devices necessitates suppression of surface states dominating the electronic properties. The absence of a stable and passive surface oxide for SiGe results in the formation of charge traps at the SiGe-oxide interface induced by GeOx. In an ideal ALD process in which oxide is grown layer by layer, the GeOx formation should be prevented with selective surface oxidation (i.e., formation of an SiOx interface) by controlling the oxidant dose in the first few ALD cycles of the oxide deposition on SiGe. However, in a real ALD process, the interface evolves during the entire ALD oxide deposition due to diffusion of reactant species through the gate oxide. In this work, this diffusion process in nonideal ALD is investigated and exploited: the diffusion through the oxide during ALD is utilized to passivate the interfacial defects by employing ozone as a secondary oxidant. Periodic ozone exposure during gate oxide ALD on SiGe is shown to reduce the integrated trap density (Dit) across the band gap by nearly 1 order of magnitude in Al2O3 (<6 × 1010 cm-2) and in HfO2 (<3.9 × 1011 cm-2) by forming a SiOx-rich interface on SiGe. Depletion of Ge from the interfacial layer (IL) by enhancement of volatile GeOx formation and consequent desorption from the SiGe with ozone insertion during the ALD growth process is confirmed by electron energy loss spectroscopy (STEM-EELS) and hypothesized to be the mechanism for reduction of the interfacial defects. In this work, the nanoscale mechanism for defect suppression at the SiGe-oxide interface is demonstrated, which is engineering of diffusion species in the ALD process due to facile diffusion of reactant species in nonideal ALD.

Conjugation of a Small-Molecule TLR7 Agonist to Silica Nanoshells Enhances Adjuvant Activity.

Stimulation of Toll-like receptors (TLRs) and/or NOD-like receptors on immune cells initiates and directs immune responses that are essential for vaccine adjuvants. The small-molecule TLR7 agonist, imiquimod, has been approved by the FDA as an immune response modifier but is limited to topical application due to its poor pharmacokinetics that causes undesired adverse effects. Nanoparticles are increasingly used with innate immune stimulators to mitigate side effects and enhance adjuvant efficacy. In this study, a potent small-molecule TLR7 agonist, 2-methoxyethoxy-8-oxo-9-(4-carboxybenzyl)adenine (1V209), was conjugated to hollow silica nanoshells (NS). Proinflammatory cytokine (IL-6, IL-12) release by mouse bone-marrow-derived dendritic cells and human peripheral blood mononuclear cells revealed that the potency of silica nanoshells-TLR7 conjugates (NS-TLR) depends on nanoshell size and ligand coating density. Silica nanoshells of 100 nm diameter coated with a minimum of ∼6000 1V209 ligands/particle displayed 3-fold higher potency with no observed cytotoxicity when compared to an unconjugated TLR7 agonist. NS-TLR activated the TLR7-signaling pathway, triggered caspase activity, and stimulated IL-1ß release, while neither unconjugated TLR7 ligands nor silica shells alone produced IL-1ß. An in vivo murine immunization study, using the model antigen ovalbumin, demonstrated that NS-TLR increased antigen-specific IgG antibody induction by 1000× with a Th1-biased immune response, compared to unconjugated TLR7 agonists. The results show that the TLR7 ligand conjugated to silica nanoshells is capable of activating an inflammasome pathway to enhance both innate immune-stimulatory and adjuvant potencies of the TLR7 agonist, thereby broadening applications of innate immune stimulators.

Band Structure Engineering of Layered WSe2 via One-Step Chemical Functionalization.

Chemical functionalization is demonstrated to enhance the p-type electrical performance of two-dimensional (2D) layered tungsten diselenide (WSe2) field-effect transistors (FETs) using a one-step dipping process in an aqueous solution of ammonium sulfide [(NH4)2S(aq)]. Molecularly resolved scanning tunneling microscopy and spectroscopy reveal that molecular adsorption on a monolayer WSe2 surface induces a reduction of the electronic band gap from 2.1 to 1.1 eV and a Fermi level shift toward the WSe2 valence band edge (VBE), consistent with an increase in the density of positive charge carriers. The mechanism of electronic transformation of WSe2 by (NH4)2S(aq) chemical treatment is elucidated using density functional theory calculations which reveal that molecular "SH" adsorption on the WSe2 surface introduces additional in-gap states near the VBE, thereby, inducing a Fermi level shift toward the VBE along with a reduction in the electronic band gap. As a result of the (NH4)2S(aq) chemical treatment, the p-branch ON-currents (ION) of back-gated few-layer ambipolar WSe2 FETs are enhanced by about 2 orders of magnitude, and a ∼6× increase in the hole field-effect mobility is observed, the latter primarily resulting from the p-doping-induced narrowing of the Schottky barrier width leading to an enhanced hole injection at the WSe2/contact metal interface. This (NH4)2S(aq) chemical functionalization technique can serve as a model method to control the electronic band structure and enhance the performance of devices based on 2D layered transition-metal dichalcogenides.

Engineering High- k/SiGe Interface with ALD Oxide for Selective GeO x Reduction.

Suppression of electronic defects induced by GeO x at the high- k gate oxide/SiGe interface is critical for implementation of high-mobility SiGe channels in complementary metal-oxide-semiconductor (CMOS) technology. Theoretical and experimental studies have shown that a low defect density interface can be formed with an SiO x-rich interlayer on SiGe. Experimental studies in the literature indicate a better interface formation with Al2O3 in contrast to HfO2 on SiGe; however, the mechanism behind this is not well understood. In this study, the mechanism of forming a low defect density interface between Al2O3/SiGe is investigated using atomic layer deposited (ALD) Al2O3 insertion into or on top of ALD HfO2 gate oxides. To elucidate the mechanism, correlations are made between the defect density determined by impedance measurements and the chemical and physical structures of the interface determined by high-resolution scanning transmission electron microscopy and electron energy loss spectroscopy. The compositional analysis reveals an SiO x rich interlayer for both Al2O3/SiGe and HfO2/SiGe interfaces with the insertion of Al2O3 into or on top of the HfO2 oxide. The data is consistent with the Al2O3 insertion inducing decomposition of the GeO x from the interface to form an electrically passive, SiO x rich interface on SiGe. This mechanism shows that nanolaminate gate oxide chemistry cannot be interpreted as resulting from a simple layer-by-layer ideal ALD process, because the precursor or its reaction products can diffuse through the oxide during growth and react at the semiconductor interface. This result shows that in scaled CMOS, remote oxide ALD (oxide ALD on top of the gate oxide) can be used to suppress electronic defects at gate oxide semiconductor interfaces by oxygen scavenging.

Thickness and Sphericity Control of Hollow Hard Silica Shells through Iron (III) Doping: Low Threshold Ultrasound Contrast Agents.

Silica particles are convenient ultrasound imaging contrast agents because of their long imaging time and ease of modification; however, they require a relatively high insonation power for imaging and have low biodegradability. In this study, 2 µm ultrathin asymmetric hollow silica particles doped with iron (III) (Fe(III)-SiO2) are synthesized to produce biodegradable hard shelled particles with a low acoustic power threshold comparable with commercial soft microbubble contrast agents (Definity) yet with much longer in vivo ultrasound imaging time. Furthermore, high intensity focused ultrasound ablation enhancement with these particles shows a 2.5-fold higher temperature elevation than with Definity at the same applied power. The low power visualization improves utilization of the silica shells as an adjuvant in localized immunotherapy. The data are consistent with asymmetric engineering of hard particle properties that improve functionality of hard versus soft particles.

MRI-guided transurethral insonation of silica-shell phase-shift emulsions in the prostate with an advanced navigation platform.

PURPOSE: In this study, the efficacy of transurethral prostate ablation in the presence of silica-shell ultrasound-triggered phase-shift emulsions (sUPEs) doped with MR contrast was evaluated. The influence of sUPEs on MR imaging assessment of the ablation zone was also investigated. METHODS: sUPEs were doped with a magnetic resonance (MR) contrast agent, Gd2 O3 , to assess ultrasound transition. Injections of saline (sham), saline and sUPEs alone, and saline and sUPEs with Optison microbubbles were performed under guidance of a prototype interventional MRI navigation platform in a healthy canine prostate. Treatment arms were evaluated for differences in lesion size, T1  contrast, and temperature. In addition, non-perfused areas (NPAs) on dynamic contrast-enhanced (DCE) MRI, 55°C isotherms, and areas of 240 cumulative equivalent minutes at 43°C (CEM43 ) dose or greater computed from MR thermometry were measured and correlated with ablated areas indicated by histology. RESULTS: For treatment arms including sUPEs, the computed correlation coefficients between the histological ablation zone and the NPA, 55°C isotherm, and 240 CEM43 area ranged from 0.96-0.99, 0.98-0.99, and 0.91-0.99, respectively. In the absence of sUPEs, the computed correlation coefficients between the histological ablation zone and the NPA, 55°C isotherm, and 240 CEM43 area were 0.69, 0.54, and 0.50, respectively. Across all treatment arms, the areas of thermal tissue damage and NPAs were not significantly different (P = 0.47). Areas denoted by 55°C isotherms and 240 CEM43 dose boundaries were significantly larger than the areas of thermal damage, again for all treatment arms (P = 0.009 and 0.003, respectively). No significant differences in lesion size, T1 contrast, or temperature were observed between any of the treatment arms (P > 0.0167). Lesions exhibiting thermal fixation on histological analysis were present in six of nine insonations involving sUPE injections and one of five insonations involving saline sham injections. Significantly larger areas (P = 0.002), higher temperatures (P = 0.004), and more frequent ring patterns of restricted diffusion on ex vivo diffusion-weighted imaging (P = 0.005) were apparent in lesions with thermal fixation. CONCLUSIONS: T1 contrast suggesting sUPE transition was not evident in sUPE treatment arms. The use of MR imaging metrics to predict prostate ablation was not diminished by the presence of sUPEs. Lesions generated in the presence of sUPEs exhibited more frequent thermal fixation, though there were no significant changes in the ablation areas when comparing arms with and without sUPEs. Thermal fixation corresponded to some qualitative imaging features.

Ultralow Defect Density at Sub-0.5 nm HfO2/SiGe Interfaces via Selective Oxygen Scavenging.

The superior carrier mobility of SiGe alloys make them a highly desirable channel material in complementary metal-oxide-semiconductor (CMOS) transistors. Passivation of the SiGe surface and the associated minimization of interface defects between SiGe channels and high- k dielectrics continues to be a challenge for fabrication of high-performance SiGe CMOS. A primary source of interface defects is interfacial GeO x. This interfacial oxide can be decomposed using an oxygen-scavenging reactive gate metal, which nearly eliminates the interfacial oxides, thereby decreasing the amount of GeO x at the interface; the remaining ultrathin interlayer is consistent with a SiO x-rich interface. Density functional theory simulations demonstrate that a sub-0.5 nm thick SiO x-rich surface layer can produce an electrically passivated HfO2/SiGe interface. To form this SiO x-rich interlayer, metal gate stack designs including Al/HfO2/SiGe and Pd/Ti/TiN/nanolaminate (NL)/SiGe (NL: HfO2-Al2O3) were investigated. As compared to the control Ni-gated devices, those with Al/HfO2/SiGe gate stacks demonstrated more than an order of magnitude reduction in interface defect density with a sub-0.5 nm SiO x-rich interfacial layer. To further increase the oxide capacitance, the devices were fabricated with a Ti oxygen scavenging layer separated from the HfO2 by a conductive TiN diffusion barrier (remote scavenging). The Pd/Ti/TiN/NL/SiGe structures exhibited significant capacitance enhancement along with a reduction in interface defect density.