Tunneling-current-induced local excitonic luminescence in p-doped WSe2 monolayers

The excitonic luminescence of monolayer molybdenum disulfide (MoS2) on a gold substrate is studied by scanning tunneling microscopy (STM). STM-induced light emission (STM-LE) from MoS2 is assigned to the radiative decay of A and B excitons. The intensity ratio of A and B exciton emission can be modulated by the tunneling current, since the A exciton emission intensity saturates at high tunneling currents. Moreover, the corrugated gold substrate introduces local strain to the monolayer MoS2, resulting in significant changes of electronic bandgap and valence band splitting. The modulation rates of strain on A and B exciton energies are estimated as -72 meV/% and -57 meV/%, respectively. STM-LE provides a direct link between exciton energy and local strain in monolayer MoS2 with a spatial resolution <10 nm.

Experiments with a scanning tunneling microscope (STM) mounted in a scanning electron microscope (SEM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144620 ◽

1986 ◽

Vol 44 ◽

pp. 636-639

Author(s):

Oliver C. Wells ◽

Mark E. Welland

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Mechanical Stability ◽

Tunneling Current ◽

Feedback System ◽

Scanning Tunneling ◽

Surface Profiling ◽

Close Proximity ◽

Metal Tip ◽

Scanning Electron

Scanning tunneling microscopes (STM) exist in two versions. In both of these, a pointed metal tip is scanned in close proximity to the specimen surface by means of three piezos. The distance of the tip from the sample is controlled by a feedback system to give a constant tunneling current between the tip and the sample. In the low-end STM, the system has a mechanical stability and a noise level to give a vertical resolution of between 0.1 nm and 1.0 nm. The atomic resolution STM can show individual atoms on the surface of the specimen.A low-end STM has been put into the specimen chamber of a scanning electron microscope (SEM). The first objective was to investigate technological problems such as surface profiling. The second objective was for exploratory studies. This second objective has already been achieved by showing that the STM can be used to study trapping sites in SiO2.

UHV-STM studies of silicon nano-pyramid growth on silicon surface at high temperature

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130353 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1144-1145

Author(s):

T. Sato ◽

S. Kitamura ◽

T. Sueyoshl ◽

M. Iwatukl ◽

C. Nielsen

Keyword(s):

High Temperature ◽

Relaxation Process ◽

Thermal Effect ◽

Bias Voltage ◽

Silicon Surface ◽

Growth Process ◽

Tunneling Current ◽

Fabrication Technique ◽

Nano Fabrication ◽

Electromigration Effect

Recently, the growth process and relaxation process of crystalline structures were studied by observing a SI nano-pyramid which was built on a Si surface with a UHV-STM. A UHV-STM (JEOL JSTM-4000×V) was used for studying a heated specimen, and the specimen was kept at high temperature during observation. In this study, the nano-fabrication technique utilizing the electromigration effect between the STM tip and the specimen was applied. We observed Si atoms migrated towords the tip on a high temperature Si surface.Clean surfaces of Si(lll)7×7 and Si(001)2×l were prepared In the UHV-STM at a temperature of approximately 600 °C. A Si nano-pyramid was built on the Si surface at a tunneling current of l0nA and a specimen bias voltage of approximately 0V in both polarities. During the formation of the pyramid, Images could not be observed because the tip was stopped on the sample. After the formation was completed, the pyramid Image was observed with the same tip. After Imaging was started again, the relaxation process of the pyramid started due to thermal effect.

A TEM study of electron tunneling in biological macromolecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125634 ◽

1987 ◽

Vol 45 ◽

pp. 140-141

Author(s):

J. A. Panitz

Keyword(s):

Stark Effect ◽

Electron Tunneling ◽

Imaging Modality ◽

Tunneling Current ◽

Biological Species ◽

Scanning Tunneling ◽

Biological Macromolecules ◽

Flat Surfaces ◽

Virus Particles ◽

Stm Images

Tunneling is a ubiquitous phenomenon. Alpha particle disintegration, the Stark effect, superconductivity in thin films, field-emission, and field-ionization are examples of electron tunneling phenomena. In the scanning tunneling microscope (STM) electron tunneling is used as an imaging modality. STM images of flat surfaces show structure at the atomic level. However, STM images of large biological species deposited onto flat surfaces are disappointing. For example, unstained virus particles imaged in the STM do not resemble their TEM counterparts.It is not clear how an STM image of a biological species is formed. Most biological species are large compared to the nominal electrode separation of ∼ 1nm that is required for electron tunneling. To form an image of a biological species, the tunneling electrodes must be separated by a distance that would normally be too large for a tunneling current to be observed.

Study of Tip-Surface Interactions in Scanning Tunneling Microscopy (STM) by Reflection Electron Microscopy (REM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180355 ◽

1990 ◽

Vol 48 (1) ◽

pp. 320-321

Author(s):

W. Lo ◽

J.C.H. Spence ◽

M. Kuwabara

Keyword(s):

High Resolution ◽

Elastic Strain ◽

Tunneling Current ◽

Surface Damage ◽

Surface Interactions ◽

Graphite Surface ◽

Scanning Tunneling ◽

Large Area ◽

Tunneling Microscopy ◽

High Resolution Tem

Work on the integration of STM with REM has demonstrated the usefulness of this combination. The STM has been designed to replace the side entry holder of a commercial Philips 400T TEM. It allows simultaneous REM imaging of the tip/sample region of the STM (see fig. 1). The REM technique offers nigh sensitivity to strain (<10−4) through diffraction contrast and high resolution (<lnm) along the unforeshortened direction. It is an ideal technique to use for studying tip/surface interactions in STM.The elastic strain associated with tunnelling was first imaged on cleaved, highly doped (S doped, 5 × 1018cm-3) InP(110). The tip and surface damage observed provided strong evidence that the strain was caused by tip/surface contact, most likely through an insulating adsorbate layer. This is consistent with the picture that tunnelling in air, liquid or ordinary vacuum (such as in a TEM) occurs through a layer of contamination. The tip, under servo control, must compress the insulating contamination layer in order to get close enough to the sample to tunnel. The contaminant thereby transmits the stress to the sample. Elastic strain while tunnelling from graphite has been detected by others, but never directly imaged before. Recent results using the STM/REM combination has yielded the first direct evidence of strain while tunnelling from graphite. Figure 2 shows a graphite surface elastically strained by the STM tip while tunnelling (It=3nA, Vtip=−20mV). Video images of other graphite surfaces show a reversible strain feature following the tip as it is scanned. The elastic strain field is sometimes seen to extend hundreds of nanometers from the tip. Also commonly observed while tunnelling from graphite is an increase in the RHEED intensity of the scanned region (see fig.3). Debris is seen on the tip and along the left edges of the brightened scan region of figure 4, suggesting that tip abrasion of the surface has occurred. High resolution TEM images of other tips show what appear to be attached graphite flakes. The removal of contamination, possibly along with the top few layers of graphite, seems a likely explanation for the observed increase in RHEED reflectivity. These results are not inconsistent with the “sliding planes” model of tunnelling on graphite“. Here, it was proposed that the force due to the tunnelling probe acts over a large area, causing shear of the graphite planes when the tip is scanned. The tunneling current is then modulated as the planes of graphite slide in and out of registry. The possiblity of true vacuum tunnelling from the cleaned graphite surface has not been ruled out. STM work function measurements are needed to test this.

The Effect of Roughness Features on Mos Surface Electric Field and Fowler-Nordheim Tunneling Behavior

MRS Proceedings ◽

10.1557/proc-473-175 ◽

1997 ◽

Vol 473 ◽

Author(s):

Heng-Chih Lin ◽

Edwin C. Kan ◽

Toshiaki Yamanaka ◽

Simon J. Fang ◽

Kwame N. Eason ◽

...

Keyword(s):

Electric Field ◽

Three Dimensional ◽

Tunneling Current ◽

Gate Oxide ◽

Oxide Thickness ◽

Interface Roughness ◽

Normal Electric Field ◽

Surface Electric Field ◽

Tunneling Behavior ◽

Nordheim Tunneling

ABSTRACTFor future CMOS GSI technology, Si/SiO2 interface micro-roughness becomes a non-negligible problem. Interface roughness causes fluctuations of the surface normal electric field, which, in turn, change the gate oxide Fowler-Nordheim tunneling behavior. In this research, we used a simple two-spheres model and a three-dimensional Laplace solver to simulate the electric field and the tunneling current in the oxide region. Our results show that both quantities are strong functions of roughness spatial wavelength, associated amplitude, and oxide thickness. We found that RMS roughness itself cannot fully characterize surface roughness and that roughness has a larger effect for thicker oxide in terms of surface electric field and tunneling behavior.

High Quality HfO2 Film and Its Applications in Novel Poly-Si Devices

MRS Proceedings ◽

10.1557/proc-716-b2.6 ◽

2002 ◽

Vol 716 ◽

Author(s):

K.L. Ng ◽

N. Zhan ◽

M.C. Poon ◽

C.W. Kok ◽

M. Chan ◽

...

Keyword(s):

Barrier Height ◽

Nonvolatile Memory ◽

Dielectric Material ◽

Tunneling Current ◽

Interface Layer ◽

Si Substrate ◽

Hfo2 Film ◽

Effective Barrier Height ◽

Effective Barrier ◽

Nonvolatile Memory Devices

AbstractHfO2 as a dielectric material in MOS capacitor by direct sputtering of Hf in an O2 ambient onto a Si substrate was studied. The results showed that the interface layer formed between HfO2 and the Si substrate was affected by the RTA time in the 500°C annealing temperature. Since the interface layer is mainly composed of hafnium silicate, and has high interface trap density, the effective barrier height is therefore lowered with increased RTA time. The change in the effective barrier height will affect the FN tunneling current and the operation of the MOS devices when it is applied for nonvolatile memory devices.

Improvement in Gate Dielectric Quality of Ultra Thin a: SiN:H MNS Capacitor by Hydrogen Etching of the Substrate

MRS Proceedings ◽

10.1557/proc-716-b4.8 ◽

2002 ◽

Vol 716 ◽

Author(s):

Parag C. Waghmare ◽

Samadhan B. Patil ◽

Rajiv O. Dusane ◽

V.Ramgopal Rao

Keyword(s):

Silicon Nitride ◽

Gate Dielectric ◽

Substrate Surface ◽

Scaling Limit ◽

Tunneling Current ◽

Chemical Vapor ◽

Poor Performance ◽

State Density ◽

Direct Tunneling Current

AbstractTo extend the scaling limit of thermal SiO2, in the ultra thin regime when the direct tunneling current becomes significant, members of our group embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. Silicon nitride can be deposited using several CVD methods and its properties significantly depend on the method of deposition. Although these CVD methods can give good physical properties, the electrical properties of devices made with CVD silicon nitride show very poor performance related to very poor interface, poor stability, presence of large quantity of bulk traps and high gate leakage current. We have employed the rather newly developed Hot Wire Chemical Vapor Deposition (HWCVD) technique to develop the a:SiN:H material. From the results of large number of optimization experiments we propose the atomic hydrogen of the substrate surface prior to deposition to improve the quality of gate dielectric. Our preliminary results of these efforts show a five times improvement in the fixed charges and interface state density.

A Novel Excitation Source Model for Analysis of Rhombic Antenna Characteristics

SOP Transactions on Wireless Communications ◽

10.15764/stowc.2014.02008 ◽

2014 ◽

Vol 1 (2) ◽

pp. 76-86

Author(s):

Fan Yin ◽

◽

Chengyou Yin

Keyword(s):

Source Model ◽

Excitation Source ◽

Antenna Characteristics

Characterization of a Resistive Path to a Gate Node Using Tunneling Current Measurements

ISTFA 2010: Conference Proceedings from the 36th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2010p0409 ◽

2010 ◽

Author(s):

Clifford Howard ◽

Sam Subramanian ◽

Kent Erington ◽

Randall Mulder ◽

Yuk Tsang ◽

...

Keyword(s):

High Resistance ◽

Tunneling Current ◽

Resistance Measurement ◽

Gate Leakage ◽

Advanced Technologies

Abstract Advanced technologies with higher gate leakage due to oxide tunneling current enable detection of high resistance faults to gate nodes using a straight forward resistance measurement.