Semiconductors and Nanotechnology

"WET NANO-BONDING OF SILICA-TO-SI AND SILICA-TO-SILICA BELOW 200°C  BY H2O CATALYSIS AND A 2-D PRECURSOR PHASE:
TMAFM, HYDROAFFINITY AND SURFACE FREE ENERGY ANALYSIS

R. Bennett-Kennett*, S. D. Whaley, N. Herbots*, C. F. Watson*, R.J. Culbertson, A. Murphy,* S. Farmer,** P. Rez, D.A. Sell,** B. Hughes, A. Acharya,
ARIZONA STATE UNIVERSITY,
Department of Physics, of Chemistry & Bio-Chemistry Tempe, AZ 85287-1504,
* SiO2 NanoTech LLC,Tempe, AZ 85282
** Marquette University, Marquette, WI
*** Caltech, Pasadena, CA

R.L. Rhoades, Scott N.  Drews 
Entrepix, Inc. Tempe AZ 85282.

Hydroxylated silica about 2.1 ± 0.1 nm thick are nucleated on OH(1x1)Si(100) as precursor phase to cross-bond directly silica to Si, and silica to silica using planarization via extended atomic terraces,  T≤ 200°C, an H2O/O2 ambient, and p ≥ 1 atm. This method, "Wet Nano-Bonding™”, relies on the Herbots-Atluri process [1] to nucleate precursor phases to bond via direct hydroxylated silica molecular cross-bridges two surfaces brought into contact at the nano-scale. 
Ordered Si2(OH)4 β-cristobalite precursor phases exhibit atomic terraces that extend to > 20 nm, in contrast to the 2 nm width in "as received" Si(100) wafers. β-cristobalite nano-phases can desorb at low temperatures (T </~ 200 °C) [3]. These ordered oxides can promote the growth of flatter, smoother, better controlled oxides at low temperatures in ambient air. When put into close contact at T≥ 200°C with oxygen-deficient phases of SiOx used in microelectronics, they can consistently nucleate a cross-bridging between the two substrates, or “nano-bonding” inter-phase [4] between various combinations Si and silica provided an H2O/O2 ambient catalyzes low temperature oxidation and nano-contacting is achieved via pressurization in the nano-bonding chamber.

[1] V. Atluri et al MRS Symp. Proc. Vol 477 (1997)
[2] N. Herbots et al. Mater. Sc. & Eng, B87 (2001), 303
[3] N. Herbots et al., US patent 6,613,617 (2003) & 7,851,365 (2011)
[4]  K.T. Queeney et al. Appl. Phys. Lett., Vol. 84, No. 4, 26 (2004)"

Chalcogenides are narrow-band gap semiconductors that have been widely used as photocatalysts. These narrow-band gap materials allow more efficient absorption of over 40% of solar energy in the visible light range, which will eventually improve its photocatalytic properties. Under visible light irradiation, these materials generate electron and hole (e/h+) pairs. Photo-generated e/h+ pairs have been utilized to split water into hydrogen and oxygen and to remove and degrade industrial, pharmaceutical and agricultural organic/inorganic/biological pollutants that have been accumulated in the environment. In this perspective review, different types of chalcogenides, namely, binary, multinary (ternary and quaternary) and chalcogenide-based heterostructures are presented briefly. This perspective review also highlights the mechanisms involved and remarkable photocatalytic activity enhancement under visible light irradiation that has been widely researched such as the photocatalytic degradation of industrial pollutants and photocatalytic inactivation of bacteria. Lastly, future prospects for the use of chalcogenides as photocatalysts and chalcogenide-based heterostructures were discussed.

Presented here is a patent in the Bulgarian register of inventions (Reg. № 41177/1978), written in Bulgarian. The patent relates to uniform deposition of semiconducting and insulating thin films in cold gas plasma. Various flat substrates can be used, semiconductor ones in particular. The claims relate to a specific configuration of the reactor chamber by which uniformity of the (static part of) gas plasma is achieved. That feature results in improved uniformity of the thus deposited thin films, as compared to the one achieved by the existing systems. The application of this method is demonstrated on Si3N4 and SiO2 thin layers deposited onto Silicon wafers, aimed for the mass production of MOS IC’s (Metal-Oxide-Semiconductor Integrated Circuits).

The invention described features one claim. The description is supported by two drawings.

The goal of this study is to investigate the effect of carbon incorporation upon thermal oxidation of Si1−x Ge x alloys and its role on strain compensation in Si1−x Ge x alloys. Si1−x Ge x and Si1−x−y Ge x C y alloys on Si(100) are grown by combined ion and molecular beam deposition and are then oxidized at 1000 °C in a dry oxygen ambient for two h. The thickness and the composition of all samples before and after oxidation are measured by Rutherford backscattering spectrometry (RBS) combined with ion channeling at 2.0 MeV and carbon nuclear resonance analysis at 4.3 MeV using 4He++ ions. In agreement with previously reported results of dry oxidation on Si1−x Ge x thin films, 2.0 MeV RBS analysis shows that a layer of SiO2 is formed on the top surface of both Si1−x Ge x and Si1−x−y Ge x C y thin films, while Ge segregates towards the top surface and at the SiO2/Si1−x Ge x and SiO2/Si1−x−y Ge x C y interfaces. However, it is observed for the first time that dry oxidation rates of Si1−x Ge x thin films decrease with increasing Ge fraction x for x≳0.20 and with increasing minimum yield. Ion channeling analysis and strain measurements indicate that the incorporation of C rather than the amount of C itself affects the dry oxidation mechanism because of its strong influence on film strain and crystalline quality. These results are discussed in conjunction with observations by secondary ion mass spectrometry, high resolution transmission electron microscopy, Fourier transform infrared spectrometry, and tapping mode atomic force microscopy.

Graphene is one of the recently discovered materials from which graphene nano-ribbon (acronym, GNR) is derived. GNR has a great impact on the nano scale field effect transistors (FET) which has been tried to demonstrate in this study. Here, we have illustrated an analytical model of GNRFET for spatial distributions of the electric potential along the channel. The analysis is performed to find out the dependences of the source-drain current on the drain voltages as well as on the back gate and top gate voltages for different geometric parameters of the device. The switching on and switching off characteristics have been demonstrated in terms of current density, channel length and gate-voltage.

In this work, the feasibility of a monolithically integrated laser and electroabsorption modulator based on the same active quantum dot epistructure is studied. The net modal gain and the absorption in the modulator were measured using the segmented contact method from 25 °C to 125 °C. The maximum of the net modal gain active region of the laser decreases from 10 cm -1 at 25 °C to 3.9 cm -1 at 125 °C. The non-optimized maximum extinction ratio of the modulator, 4.1 dB·mm -1 , is almost constant until 25 °C. The wavelengths at which the net modal gain and the change in absorption are maximum shifts with temperature by 0.04 eV.

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of e 0 , e 0 , tand, electric modulus (M 0 and M 00) and r ac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of e 0 , e 0 , tand, M 0 , M 00 and r ac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of e 0 , e 00 and tand show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of r ac and the electric modulus increase with increasing frequency. The high dispersion in e 0 and e 00 values at low frequencies may be attributed to the Maxwell–Wagner and space charge polarization. The high values of e 0 may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M 0 and M 00 reach a maximum constant value corresponding to M 1 % 1/e 1 due to the relaxation process at high frequencies, but both the values of M 0 and M 00 approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of N ss and R s of the capacitors. As a result, the change in the e 0 , e 00 , tand, M 0 , M 00 and ac electric conductivity (r ac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

A power delivery model of a probe test system used in wafer testing is presented. Designs for critical components contributing to voltage drop in the system including the PCB, the interposer the space transformer, vertical-type MEMS-based probes along with the contact resistance (CRes) were analyzed. Simulation results show that a reduction of 38% in voltage fluctuations is possible by improved designs in interconnect designs.

The effect of incorporating pairs of dopant atoms of opposite polarities into the nanowire lattice on the electrical behavior of nanowires has been presented in this paper. The dopants used are boron and phosphorus atoms. Intrinsic silicon nanowire is incapacitated with boron-phosphorus dopant atom pairs in a progressive manner, starting from one pair to nine dopant-atom pairs. The nanowire is simulated each time an additional dopant pair is introduced in the nanowire lattice to obtain current-voltage characteristics. These characteristics have been compared with that obtained by introducing similar dopants in an intrinsic germanium nanowire lattice. The power efficiencies of both intrinsic and doped silicon and germanium nanowires have been discussed towards the end of the paper.

We experimentally demonstrate transversely coupled Fabry-Perot resonators using sidewall Bragg gratings and loop mirrors as reflectors in silicon-on-insulator platform. The resonators have channel spacing of ~50 GHz, extinction ratio of ~12 dB and Q-factor of ~15350.

Enhancement of switching in nanoelectronics, Carbon Nano Tube (CNT) could be utilized in nanoscaled Metal Oxide Semiconductor Field Effect Transistor (MOSFET). In this review, we present an in depth discussion of performances Carbon Nanotube Field Effect Transistor (CNTFET) and its significance in
nanoelectronic circuitry in comparison with Metal Oxide Semiconductor Field Effect Transistor (MOSFET). At first, we have discussed the structural unit of Carbon Nanotube and characteristic electrical behaviors beteween CNTFET and MOSFET. Short channel effect and effects of scattering and electric field on mobility of CNTFET and MOSFET have also been discussed. Besides, the nature of ballistic transport and profound impact of gate capacitance along with dielectric constant on transconductance have also have been overviewed. Electron ballistic transport would be the key in short channel regime for high speed switching devices. Finally, a comparative study on the characteristics of contact resistance over switching capacity between CNTFET and MOSFET has been addressed.

Ion Beam Analysis (IBA) using 4He+ ion channeling combined with Nuclear Resonance Analysis (NRA) and 3DMultiString computer simulations detect order in silicon dioxide (SiO2) nucleated on (1×1) Si(100) via the Herbots-Atluri clean (U.S. patent 6,613,677) in air at 300 K.  Alignment of the SiO2 to Si(100) is also supported by 10 keV Reflection High Energy Electron Diffraction (RHEED). Infrared spectroscopy of ordered oxides exhibit a constant, well-defined frequency of optical absorption across a 1 nm thickness in the interfacial region near Si, supporting the presence of a well defined bond-length and stoichiometry as detected by IBA and RHEED. Comparison between HRTEM and ellipsometry measurements show that the HRTEM thickness is significantly lower, by 30%, when compared to the thickness measured by ellipsometry, indicating a change in optical properties. In this work IBA is combined with 3DMultiString to identify a new heteroepitaxial nanophase of tetragonally distorted β-cristobalite SiO2 (annotated β-c SiO2) extending to a critical thickness of 2 nm from the (1×1) Si (100)/β-c SiO2 interface to the β-c SiO2 /amorphous SiO2 interface (annotated β-c SiO2/a-SiO2).  3DMultiString simulations of IBA data taken on the newly identified β-c SiO2/(1×1) Si(100) interphase includes channeling along the three <100>, <110>, and <111> axes of Si (100) in combination 16O(α, α)16O 3.045 MeV NRA to measure oxygen areal densities corresponding to nm-thick films. In this manner, the critical thickness of the new heteroepitaxial β-c SiO2 nanophase can be established as a function of oxygen coverage.

Si1-x-y ,GexCy is a novel group IV semiconductor alloy with interesting possibilities for strain modification and bandgap
engineering. To investigate the growth kinetics of this new semiconductor, heteroepitaxial Si1-x-y ,GexCy films were grown
on 4 in. Si(100) wafers by combined ion and molecular beam deposition at temperatures between 450 and 560°C.
Transmission electron microscopy (TEM) combined with diffraction show that the films, 1000 ± 220 A thick, are single
phase heteroepitaxial cubic diamond solid solutions. For films with a Si : Ge ratio of 7 : 3 the defect density is low for carbon
concentrations less than I%. The (Xmin) minimum yield increases from 0.13 to 0.89 as the carbon concentration increases
from 0.5 to 3%. For low C concentrations, the channeling yield increases with depth indicating that the defect density
increases near the film substrate interface, which is characteristic of partial film relaxation. For C concentrations of 2% and
higher the defect density is uniformly high throughout the films indicating that defects are uniformly nucleated throughout
the film during growth. Infrared spectroscopy measurements show that the Si-C bond length distribution broadens as the
carbon concentration increases and also shows that carbon exhibits a higher substitutionality for a growth temperature of
450°C than for 560°C. A possible interpretation of these results is that the high local strain associated with the Si-C bonds
deteriorates the elastic properties of Si1-x-y ,GexCy, making it more susceptible to relaxation and defect nucleation than
Si1-x-y ,GexCy I under similar strain and growth temperatures.

Graphene is one of the recently discovered materials from which graphene nano-ribbon (acronym, GNR) is derived. GNR has a great impact on the nano scale field effect transistors (FET) which has been tried to demonstrate in this study. Here, we have illustrated an analytical model of GNRFET for spatial distributions of the electric potential along the channel. The analysis is performed to find out the dependences of the source-drain current on the drain voltages as well as on the back gate and top gate voltages for different geometric parameters of the device. The switching on and switching off characteristics have been demonstrated in terms of current density, channel length and gate-voltage.

We investigate the energy conversion process and subsequent thermal and bit-writing performance of a plasmonic near-field transducer (NFT) under steady-state operation within heat-assisted magnetic recording (HAMR) devices. The NFT is composed of metal-insulator-metal (MIM) layers that are designed to localize heating and produce optimal thermal gradients in order to relieve parasitic heating effects in the NFT. The thin-film MIM structure confines the electromagnetic energy in the down-track direction while cross-track confinement is achieved by tapering the insulator feature of the MIM. A comparative analysis using Gold and a number of novel Au alloys is undertaken. Modeled performance shows excellent thermal spot confinement (50 × 50 nm2) of temperatures above 650 K at an input laser power of 830 nm of less than 5 milliwatts. In addition, micromagnetic simulations using a stochastic Landau-Lifshitz-Bloch equation yield excellent signal to noise ratio with minimum jitter of under 2 nm when recording.

A CMOS-compatible plasmonic multimode filter capable of working in the O, E, S, C, L, and U optical communication bands is analysed. The device consists of a hybrid plasmonic waveguide with metal segments. By properly designing the segments, it is possible to pass a particular mode and diffract the others. The results of the analysis show that the device has an extinction ratio over 20 dB and an insertion loss of less than 1.6 dB across the mentioned optical communication bands.

Highly relaxed GaN nanodots and submicron ridges have been selectively grown in the NSAG regime using MOVPE on lattice mismatched 6H–SiC and AlN substrates. 2D real space and 3D reciprocal space mapping was performed with a CCD detector using 10.4 keV synchrotron X-ray radiation at the 2-ID-D micro-diffraction beamline at Advanced Photon Source (APS). Calibration procedures have been developed to overcome the unique challenges of analyzing NSAG structures grown on highly mismatched sub-strates. We studied crystallographic planar bending on the submicron scale and found its correlation with strain relaxation in the NSAG ridges.

Ultrafast soliton switching in a two-core fiber coupler is studied by controlling the coupling coefficients of the fiber. The numerical investigation of all optical soliton switching is done by using split step Fourier transformation algorithm. An extended study is done for coupled mode NLSE and the behaviour of the launched pulse is studied by controlling the coupling coefficient (k)and it is found that faster switching takes place by rightly controlling the coupling coefficient of the fiber coupler.

Epitaxial growth requires an initial surface that is ordered and as free as possible of contaminants such as C, 0, or
metallic impurities. Wet chemical etching of Si( 111) wafers by a solution of HF in alcohol after a modified RCA clean, has
been shown to produce (1 X 1) H-terminated hydrophobic Si surfaces that are ordered at room temperature and can be
desorbed at 200°C in UHV. Less is known about a similar treatment on Si(lO0) wafers, more commonly used in
semiconductor technology. However, high temperature (T> 800°C) thermal desorption of the native oxide on Si(lO0) is
known to induce detrimental effects such as surface roughness, precipitation and dopant segregation. Therefore, this study is
motivated by the development of a low-temperature (T < 600°C) surface cleaning method for Sit 100). RBS combined with
ion channeling and nuclear reaction analysis is conducted to measure the coverage of C, 0, and H as well as the residual
disorder at the surface at different steps of wet chemical cleaning prior to low temperature desorption. Hydrogen is detected
by the forward elastic recoil of H by 4He2+ at 2.8 MeV. 0 and C are detected by nuclear reaction analysis (NRA) at 3.05
and 4.265 MeV, respectively, in combination with ion channeling along the Si( 111) direction to increase the detection
sensitivity for C and 0 as well as to measure the Si surface peak to correlate it to surface disorder. Atomic force microscopy
of these surfaces has shown different degrees of roughness in addition to defect formation and is correlated to the ion beam
analysis results. Our results indicate a strong dependence of final H-passivation on the pretreatment of the Si surfaces before
the final dip in the HE/alcohol solution.