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We do inelastic electrical tunneling spectroscopy (IETS) to provide information concerning the vibrational and excitational modes present in silicon dioxide and phonon modes of the electrodes, and of silicon dioxide in metal-oxide-silicon tunnel junction. We analyze the phonon spectra coming from different parts of the metal-oxide-semiconductor (MOS) junction: the aluminum gate, the SiO2 ultrathin film, and the silicon substrate. We compare the phonon modes for the (100) and (111) silicon orientations. We show that IETS can reveal the modifications of Si-SiO2 interface induced by electrical stresses. After a constant voltage stress, the silicon longitudinal phonon modes are significantly shifted in energy, while the transversal phonon modes stay unaffected. Interface healing after annealing is also observed by IETS. These features make IETS a useful tool for MOS reliability studies.

We report on inelastic electron tunneling spectroscopy of a tunneling metal–oxide–semiconductor (MOS) device over an extended energy range compared to previous results. We have clearly observed the vibrations of the hydrogen-passivated (111)Si Pb center in this extended energy range. The assignment of this mode has been confirmed by a comparison with infrared experiments. Capabilities and limitations of the technique to detect and observe molecular vibrations in tunneling MOS devices are discussed.

Ultrathin amorphous SiO2 films are radio frequency sputter deposited onto thin film gold electrodes and incorporated as the insulating barrier in metal/insulator/metal tunnel junctions of the type Au/SiO2/Pb. Inelastic electron tunneling spectra (IETS) recorded at 4.2 K reveal characteristic zero bias anomalies associated with rapid variations in the Pb density of states on either side of the superconducting gap which shows unequivocally that tunneling is the primary conduction mechanism through the junctions at this temperature. Full IET spectra reported are essentially identical to those previously recorded for similar SiO2 films on aluminum. Atomic force and scanning tunneling microscope images of the SiO2 and underlying gold films are also presented; these data confirm that the SiO2 films are sufficiently uniform and continuous for IETS.

Inelastic electron tunneling spectroscopy (IETS) is used to record the vibrational spectra of thin films of amorphous SiOx prepared by radio‐frequency planar magnetron sputter deposition in argon. The SiOx films are incorporated as the insulating barriers in aluminium SiOx/lead tunnel junctions, with no prior or subsequent oxidation of the aluminium films. Peak assignments are presented by comparison with infrared, Raman, and neutron scattering data for bulk silica, and a plausible stoichiometry is proposed. The SiOx barriers can be considered as model glass substrates for further adsorption studies, and hence extend the analytical capabilities of IETS.

Tunneling measurements were performed at 4.2 K to investigate metal‐insulator‐silicon junctions with very thin silicon oxide or silicon nitride layers (2–5 nm) as tunneling barriers. For the measurements at 4.2 K highly degenerate P‐ or B‐doped Si samples were used. Silicon oxide layers were produced by oxidation of Si in dry oxygen at 600 °C or by plasma deposition in an oxygen glow discharge. Silicon nitride films were prepared by nitridation in a NH3 discharge. The effects of interface states, the Si doping density, the metal of the gate electrode and the tunneling barrier material on the tunneling conductivity were studied systematically. Changes in the conductivity were found to be related to changes in the density of interface states, caused by annealing processes or by high‐field stress. Vibrational modes of phonons and impurities in the structures were detected by inelastic electron tunneling spectroscopy. Using this approach a direct correlation between the increase in the density of interface st...

Dynamic conductance dI/dV and inelastic electron tunneling spectroscopy (IETS) d 2I/dV 2 have been measured at different temperatures for double barrier magnetic tunnel junctions with a thin top MgO layer. The resistance in the antiparallel state exhibits a normal tunnel-like behavior, while the resistance in the parallel state shows metallic-like transport, indicating the presence of pinholes in the thin top MgO layer. Three IETS peaks are the zero-bias anomaly, interface magnons, and barrier phonons in both the parallel and antiparallel states. The zero-bias anomaly is the strongest peak in the parallel state and its intensity decreases with temperature. The magnon has the largest intensity in the antiparallel state and its intensity also decreases with temperature. The origins of the dips and peaks in the dI/dV-V curve are also discussed.

A practical approach based on current-voltage characteristics measurements for detecting inelastic components ΔI of tunneling current flowing through a single-molecule junction was developed. Positive and negative ΔI was obtained for Au single atom contacts and single-molecule tunneling junctions, respectively, the discrepancy of which was attributed to the difference in the total effects of elastic and inelastic processes on the junction conductance. Numerically deduced ΔI spectra were found to allow single-molecule fingerprinting, thereby proving the capability of direct-current inelastic electron tunneling spectroscopy analysis as a simple technique for discriminating current-carrying single-molecules residing in an electrode gap.

Defects and traps in strained-Si n-type metal-oxide-semiconductor field effect transistors (MOSFETs) are studied in detail. The inelastic electron tunneling spectroscopy (IETS) technique is shown to be capable of probing traps in ultrathin gate dielectrics and obtain the energies and spatial locations of the traps. Detailed analyses of electrical stress-induced build-up of traps and electrically active bonding defects and identification of the trap-features including trap-assisted conduction and charge-trapping have been performed. The location and energies of the traps are estimated from the IETS spectra measured at both bias polarities. Identification of the acoustic and optical phonon modes (inelastic) as well as trap-features (elastic) helps in better understandings of the complex transport-mechanisms in gate dielectrics on strained layers.

We investigated the dynamic conductance and inelastic electron tunneling spectroscopy in MgO-based double barrier magnetic tunnel junctions with Co50Fe50/Co40Fe40B20 hybrid free layers. The tunneling is coherent through the MgO (001) barriers but nonresonant, and the highest tunneling magnetoresistance reaches 260% at 2 K. Based on the detailed discussion of the tunneling mechanisms, the double-barrier junctions investigated here can be considered as two single-barrier junctions in series.

We have investigated (110) CrO2/natural barrier/Co magnetic tunnel junctions for their barrier and magneto-transport properties. A negative tunnel magnetoresistance (TMR) of over 5% was observed in micro-fabricated devices at 4.2 K, which is comparable to TMR values obtained with (100) CrO2. Both transport and cross-sectional transmission electron microscopy analysis reveal a natural barrier thickness 3.5 ± 0.5 nm. However, we obtain a low effective barrier height of 0.4 eV from transport measurements. The inelastic electron tunneling spectroscopy showed significant bias dependence with peak positions showing vibrational modes, which deviate from stoichiometric Cr2O3. We conclude that the transport characteristics are controlled by defects within the natural barrier, consistent with recent theoretical reports.

We present the measurement of charge transport through phenylene conjugated molecules using electromigrated nanogap junctions. To elucidate the intrinsic transport properties of the conjugated molecular junctions, a variety of molecular transport techniques were performed at low temperature, including inelastic electron tunneling spectroscopy, temperature- and length-variable transport measurements, and transition voltage spectroscopy. Such a self-consistent characterization of the molecular junction demonstrates the observation of intrinsic molecular properties in these junctions.

Two techniques for removing the background in inelastic electron tunneling spectroscopy (IETS) have been examined in detail. The first of these uses a polynomial least‐squares routine to fit a smooth curve to the data on either side of the IETS peak, while the second relies on differential inelastic electron tunneling spectroscopy (DIETS) to subtract one spectrum from another in order to remove some unwanted IETS peaks. Both procedures were applied to spectra obtained from Al‐Pb junctions with the lead normal and superconducting. One finds that it is easier to determine the background when the normal rather than superconducting lead is used, as the superconducting line shape has a broad undershoot. The intensity results shown here indicate that failure to consider the undershoot may result in errors as large as 30%. A comparison of theoretical and experimental line shapes is made for data with both normal and superconducting electrodes.

A comparison is made of inelastic electron tunneling spectroscopy results for the chemisorption of formic acid into into two different surfaces. Details of the spectra are used to confirm that one surface is alumina and the other aluminum. A formate ion spectrum is obtained in both instances but the aluminum surface shows both greater spectral intensity and a slight shift to higher energies for the peaks. In the case of the aluminum surface the peak intensities are the same for both bias polarities as expected in the case of a single homogeneous barrier. For the alumina surface, on the other hand, there is an asymmetry in peak intensity due to the two insulator barriers.

Low energy inelastic electron tunneling spectra are presented for thermally formed oxides on copper films. Thinner oxide tunnel barriers are observed to contain interfacial gradients as evidenced by spectral intensity asymmetries between forward and reverse bias, whereas thicker oxides appear to be more uniform in composition. Spectral results are in good qualitative agreement with reported studies of bulk cuprous oxides, and the semiconducting nature of the oxide layers is reflected in a negative temperature coefficient of resistivity of the tunnel junctions.