Search

Discovery of ferroelectricity in HfO

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

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 sp

The use of a heavier noble gas such as Kr in atomic layer annealing results in higher crystallinity due to higher momentum transfer leading to a more localized and intense surface heating effect occurring over picosecond timescales.

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.

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.

The feasibility of using selective thermal cobalt metal (Co) atomic layer deposition (ALD) as high density Cu–Cu interconnect bonding is demonstrated at a low temperature (200 °C) and with minimal surface pretreatment. A Cu/Gap/Cu structure, which emulates 3-D ICs stacking is fabricated. Cobalt ALD showing seamless interconnection between copper (Cu) pads with 30- $\mu \text{m}$ pitch is demonstrated with greater than 90% yield through electrical measurements, SEM inspection, EDS, and focused ion beam (FIB) cross section.

A Cu-Cu bonding approach using low temperature (200 °C) selective Co ALD is demonstrated for Cu pads that are separated by 200 nm. The bonding testbed is characterized before and after Co ALD by SEM and EDS to confirm the feasibility of the approach. AFM and XPS are used to measure the selectivity of Co ALD on Cu and SiO 2 surfaces.

A low temperature (300°C–350°C) TiN thermal ALD process using titanium tetrachloride (TiCl 4 ) and anhydrous hydrazine was developed to yield films with resistivities below 200 μohm-cm. Surface treatments such as Ar plasma and atomic hydrogen were applied to further reduce the surface impurities including all halogens. These experiments indicate that minimizing oxygen concentration using an ultra-clean ALD process with minimum background oxidants and high purity precursors are keys in producing TiN thin films with low resistivity.

Continuous, uniform, and sub-10 nm Al2O3 high-K dielectrics upon two-dimensional exfoliated multilayer MoTe2 are realized by atomic layer deposition (ALD) based on a nucleation layer (NL) prepared by the ozone-based process, interfacial AlN, and low-temperature (low-T) physical adsorption. The NLs gives rise to significant reduction of the leakage current in the sub-10 nm Al2O3 high-K dielectrics as shown by conductive atomic force microscopy. For the ozone-based NL, X-ray photoelectron spectroscopy (XPS) reveals the oxidation of MoTe2 which is detrimental to the electrical properties of MoTe2. For the AlN NL, XPS reveals that Mo N bonds were formed without Mo O bonds and no chemical shift appeared in Te-3d XPS spectrum, indicating the AlN NL did not result in the MoTe2 oxidation but instead the formation of an MoN layer. For the low-T NL, the XPS spectra of MoTe2 are the same as those of the as-exfoliated MoTe2 flake, consistent with the absence of chemical reactions during low-T physical adsorption. The result demonstrates that the NLs prepared by the low-T physical adsorption and the interfacial AlN are effective and favorable for nucleating high-quality high-K gate dielectrics on MoTe2 transistors.

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.

A novel method for passivating the interface between Si0.7Ge0.3 using an in-situ downstream RF plasma consisting of a nitrogen-rich mixture of H2 and N2 gases at 250 °C prior to atomic layer deposition (ALD) of Al2O3 and HfO2 was demonstrated. XPS spectra of the interface with Al2O3 indicated the presence of a nitride layer enriched in SiONx and depleted in Ge relative to the substrate. The electrical properties of this interface were characterized using I-V and variable frequency C-V measurements of MOS capacitors. The N2/H2 plasma passivation process produced a reduced density of interface trap states (Dit) and lower gate leakage compared with ex-situ HF clean and sulfur passivation for Al2O3 gate oxides. The lowered leakage current and Dit observed compared with HF(aq) or sulfur-passivated surfaces were consistent with enhanced oxide nucleation due to N2/H2 plasma passivation lowering carbon surface contamination and dangling bonds. TEM/EELS analysis of the interface was consistent with the presence of a thin interfacial nitride layer suppressing the formation of Ge O bonds at the interface to form an SiOx-rich interlayer (IL).

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.

Al2O3 and Al2O3/HfO2 bilayer gate stacks were directly deposited on the surface of 2D materials via low temperature ALD/CVD of Al2O3 and high temperature ALD of HfO2 without any surface functionalization. The process is self-nucleating even on inert surfaces because a chemical vapor deposition (CVD) component was intentionally produced in the Al2O3 deposition by controlling the purge time between TMA and H2O precursor pulses at 50 °C. The CVD growth component induces formation of sub-1 nm AlOx particles (nanofog) on the surface, providing uniform nucleation centers. The ALD process is consistent with the generation of sub-1 nm gas phase particles which stick to all surfaces and is thus denoted as nanofog ALD. To prove the ALD/CVD Al2O3 nucleation layer has the conformality of a self-limiting process, the nanofog was deposited on a high aspect ratio Si3N4/SiO2/Si pattern surface; conformality of >90% was observed for a sub 2 nm film consistent with a self-limiting process. MoS2 and HOPG (highly oriented pyrolytic graphite) metal oxide semiconductor capacitors (MOSCAPs) were fabricated with single layer Al2O3 ALD at 50 °C and with the bilayer Al2O3/HfO2 stacks having Cmax of ∼1.1 µF/cm2 and 2.2 µF/cm2 respectively. In addition, Pd/Ti/TiN gates were used to increase Cmax by scavenging oxygen from the oxide layer which demonstrated Cmax of ∼2.7 µF/cm2. This is the highest reported Cmax and Cmax/Leakage of any top gated 2D semiconductor MOSCAP or MOSFET. The gate oxide prepared on a MoS2 substrate results in more than an 80% reduction in Dit compared to a Si0.7Ge0.3(0 0 1) substrate. This is attributed to a Van der Waals interaction between the oxide layer and MoS2 surface instead of a covalent bonding allowing gate oxide deposition without the generation of dangling bonds.

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.

Highly selective deposition of MoSix on Si in preference to SiO2 and SiNx was achieved via atomic layer deposition (ALD) using MoF6 and Si2H6 at 120 °C. The selectivity was enabled by the lack of chemical reactivity between the reactants and the SiO2 and SiNx substrates. In contrast, MoF6 nucleated in a self-limiting manner on H-terminated Si, and a following Si2H6 exposure reduced MoFx to Mo0 which is consistent with Mo-Si bond formation. X-Ray photoelectron spectroscopy (XPS) revealed that the 5 ALD cycles of MoF6 and Si2H6 selectively deposited a substoichiometric MoSi2 film on the Si substrate in contrast to previous results showing a nearly pure Mo deposition. Extra Si2H6 doses on the substoichiometric MoSi2 film incorporated more Si into the film without disturbing the inherent selectivity over SiO2 and SiNx. A depth-profiling study showed that the bulk of the film has Si/Mo = 1.7–1.9 with

Thermal ALD of TaNx and TiNx films was performed using hydrazine (N2H4) as a reactive N-containing source. Ultralow temperature (100 °C and 300 °C) growth of TaNx was observed using N2H4 and tris(diethylamido)(tert-butylimido) tantalum (TBTDET); XPS showed nearly stoichiometric Ta3N5 films were deposited with below 10% O and 5% C incorporation. Stoichiometric TiNx films grown at 300 °C with tetrakis(dimethylamido) titanium (TDMAT) showed an RMS roughness below 2 nm consistent with good nucleation density. High conductivity nitride films were grown by a thermal low-temperature TiNx ALD process using anhydrous N2H4 and titanium tetrachloride (TiCl4) from 300 to 400 °C; uniform, nearly stoichiometric films of 0.44 nm RMS roughness were deposited. Compared to NH3 grown films, XPS confirmed N2H4 grown films contained fewer O, C, and Cl impurities consistent with lower resistivities being observed with N2H4. The data is consistent with N2H4 serving as a reducing agent and a good proton donor to Ta and Ti ligands.

The atomic layer deposition of ruthenium has been previously reported with a wide variety of precursors. However, the search for a Ru ALD process that can deposit a film with a resistivity close to that of bulk Ru (~7 μΩ • cm) is ongoing, with an emerging interest in processes that can selectively deposit low-resistance Ru films. In this work, the grain structure and resistivity relationship for Ru ALD precursors Ru(IHD) 2 (CO) 2 and Ru(CpEt) 2 using O 2 as a coreactant is investigated using electrical measurements by four-point-probe, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction/reflectometry (XRD/XRR).

Endurance is a key material performance metric for device and memory applications and is diminished due to defect formation. Defects alter material properties and relative phase stability, adversely affecting the reliability of devices. Ferroelectric field-effect transistors (FEFETs) have metal-insulator-semiconductor (MIS where I=ferroelectric) gate stacks which typically show unsatisfactory endurance of about 10 5 cycles, [1] while metal-insulator-metal (MIM where I=ferroelectric) capacitors can demonstrate endurance up to 10 12 . Adding a linear dielectric (DE) interlayer at the FE-semiconductor interface may enhance the endurance by suppressing defect formation due to oxygen vacancies, [1] but the electrostatic role of the DE interlayer has not been clearly examined yet. Here, DFT is employed to develop an atomic and electronic level understanding of the behavior of atoms in MIM and MIS stack models with and without DE interlayers due to polarization switching.

To realize superior electrostatic control, a gate oxide bilayer for carbon nanotubes (CNT) is employed consisting of a 0.35 nm interfacial dielectric (k=7.8) and 2.5 nm high-k ALD dielectric (k=24). Using experimentally measured dielectric constants on sp2 carbon and minimum oxide thickness on CNT, a COX on CNT of 2.94×10-10 F/m is calculated for top-gate geometry. Gate leakage sub-1 pA/CNT is measured at 0.7V, better than the sub-5 nm node technology target. Top-gated carbon nanotube field effect transistors in this paper have 65 mV/dec subthreshold slope and DIBL as low as 20 mV/V at 15 nm gate length. Negligible hysteresis and no degradation in drive current from the top-gate process is observed. TCAD modeling predicts this approach will enable 68 mV/dec for top-gate CNFET with 10 nm L G , 1 nm CNT diameter and 250 CNT/μm, revealing a path to energy and performance gains from a CNT transistor technology.

The atomic layer deposition of cobalt using Co(DAD) 2 and tertiary-butyl amine (TBA) has nearly infinite selectivity (>1000 cycles) on metal vs. insulator (SiO 2 or low-k SiCOH) planar samples. However, on patterned samples, selectivity under identical ALD conditions is limited, due to the diffusion of molecularly-adsorbed metal precursor from reactive to non-reactive surfaces. Four strategies have been found to improve Co ALD selectivity: adding a passivant to remove insulator defect sites, increasing the purge time, decreasing the precursor dose, and periodic annealing. The periodic annealing technique allows reabsorption of the Co nuclei from the insulator surface to the growth surface and is consistent with a low temperature reflow process.

The low-temperature ( 2 H 4 ) or tris(dimethylamido) aluminum (TDMAA) and anhydrous N 2 H 4 with an argon plasma treatment where the ion energy is precisely controlled. High-quality AlN films are deposited with large grain size and low oxygen/carbon contamination and can be used as a templating layer for further high speed AlN film growth.

The atomic layer deposition of cobalt using Co(DAD) 2 and tertiary-butyl amine (TBA) has nearly infinite selectivity (>1000 cycles) on metal vs. insulator (SiO 2 or low-k SiCOH) planar samples. However, on patterned samples, selectivity under identical ALD conditions is limited, due to the diffusion of molecularly-adsorbed metal precursor from reactive to non-reactive surfaces. Four strategies have been found to improve Co ALD selectivity: adding a passivant to remove insulator defect sites, increasing the purge time, decreasing the precursor dose, and periodic annealing. The periodic annealing technique allows reabsorption of the Co nuclei from the insulator surface to the growth surface and is consistent with a low temperature reflow process.

Direct, atomic-scale visualization of polarization switching in a functional, polycrystalline, binary oxide via insitu high-resolution transmission electron microscopy (HRTEM) biasing is reported for the first time. Antiferroelectric (AFE) ZrO 2 was used as the model system, which is important for commercial DRAMs and as emerging NVMs (through work-function engineering). We observed (1) clear shifting and coalescing of domains within a single grain, and (2) dramatic changes of the atomic arrangements and crystalline phases-both at voltages above the critical voltage measured for AFE switching. Similar synergistic in-situ structural-electrical characterization can pave the way to understand and engineer microscopic mechanisms for retention, fatigue, variability, sub-coercive switching and analog states in ferroelectric and AFE-based memory devices.

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 (

We demonstrate a novel ferroelectric (FE) superlattice based multi-level cell (MLC) memory, which outperforms previous multi-state FE memory implemented using partial polarization switching, from the standpoint of device-to-device variation. We show that the FE superlattice consisting of alternate FE and dielectric (DE) thin layers provides a scalable approach for MLC implementation because: 1) the superlattice constructs controlled layer-by-layer polarization switching in the constituent FE layers; 2) the number of FE layers equals the number of stored bits; and, finally, (3) the switching of all the domains in a given coercive field (E C ) distribution associated with one isolated peak suppresses the variation induced by partial polarization switching. Based on these, we experimentally demonstrate a 2-bit/cell FE superlattice memory and simulate a 3-bit/cell memory with excellent device-to-device variation.

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 GeOx. This interfacial oxide can be decomposed using an oxygen-scavenging reactive gate metal, which nearly eliminates the interfacial oxides, thereby decreasing the amount of GeOx at the interface; the remaining ultrathin interlayer is consistent with a SiOx-rich interface. Density functional theory simulations demonstrate that a sub-0.5 nm thick SiOx-rich surface layer can produce an electrically passivated HfO2/SiGe interface. To form this SiOx-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...

Comprehensive Density-Functional Theory (DFT) Molecular Dynamics (MD) simulations were performed to investigate interfaces between a-HfO2 and SiGe or Ge semiconductors with fully-stoichiometric a-SiO2 or sub-oxide SiO interlayers. The electronic structure of the selected stacks was calculated with a HSE06 hybrid functional. Simulations were performed before and after hydrogen passivation of residual interlayer defects. For the SiGe substrate with Ge termination prior to H passivation, the stacks with a-SiO suboxide interlayer (a-HfO2/a-SiO/SiGe) demonstrate superior electronic properties and wider band-gaps than the stacks with fully coordinated a-SiO2 interlayers (a-HfO2/a-SiO2/SiGe). After H passivation, most of the a-HfO2/a-SiO2/SiGe defects are passivated. To investigate effect of random placement of Si and Ge atoms additional simulations with a randomized SiGe slab were performed demonstrating improvement of electronic structure. For Ge substrates, before H passivation, the stacks with a SiO suboxide interlayer (a-HfO2/a-SiO/Ge) also demonstrate wider band-gaps than the stacks with fully coordinated a-SiO2 interlayers (a-HfO2/a-SiO2/Ge). However, even for a-HfO2/a-SiO/Ge, the Fermi level is shifted close to the conduction band edge (CBM) consistent with Fermi level pinning. Again, after H passivation, most of the a-HfO2/a-SiO2/Ge defects are passivated. The stacks with fully coordinated a-SiO2 interlayers have much stronger deformation and irregularity in the semiconductor (SiGe or Ge) upper layers leading to multiple under-coordinated atoms which create band-edge states and decrease the band-gap prior to H passivation.

Low-temperature sequential exposures of N2H4 and BCl3 have been performed on Si0.3Ge0.7(001), Cu, and HOPG surfaces at 350 °C. A novel BN ALD process has been achieved on Si0.3Ge0.7(001) with 60 cycles of BN ALD producing a uniform, pinhole-free thin film with low contamination, as characterized with XPS and AFM. On Cu and Si0.3Ge0.7(001), XPS spectra indicated a near stoichiometric BN film. While AFM imaging indicated the deposition on Cu yielded nanometer-scale etching, conformal deposition was observed on Si0.3Ge0.7(001). The BN ALD also nucleated on inert HOPG via step edges. In situ STM imaging showed that cyclic exposures at 350 °C were able to decorate step edges with features ∼2 nm tall and ∼200 nm wide, indicating the propensity for BN to grow in the planar direction. The N2H4 and BCl3 ALD allows for the deposition of low oxygen, low carbon films, but to avoid etching, the growth should be nucleated by N2H4, since exposure to BCl3 can result in the formation of volatile Cl-containing surface species on many substrates. Therefore, the formation of a stable surface nitride prior to BCl3 exposure is necessary to prevent formation and desorption of volatile species from the substrate.

Background Retained foreign bodies (RFOs) have substantial clinical and financial consequences. In laparoscopic surgery, RFOs can be a cause of needing to convert a minimally invasive surgery (MIS) procedure to an open operation. A coating for surgical models was developed to augment localization of needles using fluorescence appropriate for open and minimally invasive surgeries procedures. Methods An epoxy matrix containing both dansyl chloride and indocyanine green was coated as visible and near infrared labels, respectively. With ultraviolet excitation, dansyl chloride emits green fluorescence and with NIR excitation, the ICG dye emits radiation observable with specialized near infrared capable laparoscopes. To evaluate the coatings, open and laproscopic surgeries were simulated in rabbits. Surgeons blinded to the type of needles (coated or non-coated) were timed while finding needles in standard conditions and with the use of the adjunct coatings. Control needles not located within 300 seconds were researched with the corresponding near infrared or ultraviolet light. Localization time was evaluated for statistical significance, P Results All dual dye coated needles searched utilizing the near infrared camera (n = 26) or ultraviolet light (n = 26) were located within 300 seconds. Conversely, 9 needles in both control settings (no dye usage) were not located within 300 seconds. Mean time to locate control needles in open surgery and laparoscopic surgery was statistically 2-3× greater than time to localization with the use of dye as an adjunct (P = .0027 open, P Conclusion Incorporation of a dual-dye fluorescent coating on surgical needles improved the efficiency of locating needles, may minimize the need to convert minimally invasive surgeries procedures to open, and may decrease the consequences of a missed RFO.

An on-demand long-lived ultrasound contrast agent that can be activated with single pulse stimulated imaging (SPSI) has been developed using hard shell liquid perfluoropentane filled silica 500-nm nanoparticles for tumor ultrasound imaging. SPSI was tested on LnCAP prostate tumor models in mice; tumor localization was observed after intravenous (IV) injection of the contrast agent. Consistent with enhanced permeability and retention, the silica nanoparticles displayed an extended imaging lifetime of 3.3±1 days (mean±standard deviation). With added tumor specific folate functionalization, the useful lifetime was extended to 12 ± 2 days; in contrast to ligand-based tumor targeting, the effect of the ligands in this application is enhanced nanoparticle retention by the tumor. This paper demonstrates for the first time that IV injected functionalized silica contrast agents can be imaged with an in vivo lifetime ~500 times longer than current microbubble-based contrast agents. Such functionalized long-lived contrast agents may lead to new applications in tumor monitoring and therapy.