scholarly journals The Nature of CVC Nonlinearity in Low-Voltage Scanning Tunneling Spectroscopy of Semiconductors

2021 ◽  
Vol 248 ◽  
pp. 01008
Author(s):  
A.I. Loskutov ◽  
A.M. Mandel ◽  
E.E. Karpova ◽  
V.B. Oshurko ◽  
S.G. Veselko ◽  
...  
Keyword(s):  
Low Voltage ◽  
Preexponential Factor ◽  
Scanning Tunneling Spectroscopy ◽  
Structural Defects ◽  
Scanning Tunneling ◽  
Scanning Tunnelling Microscope ◽  
Tunnel Current ◽  
Current Voltage ◽  
Tunnelling Current ◽  
Voltage Scanning

A new model of field emission in a scanning tunnelling microscope was developed. The model describes the tunnelling current from a surface of semiconductor (semimetal) and allows estimating the preexponential factor in the expression for the tunneling probability. It is shown that this factor is directly related to the degree of localization of the electron density and determines the shape of the local tunnel current-voltage characteristics (LTCVCs) at low voltages. The model allows separating the contributions of surface electronic states of different symmetry (dimension) of the tunnelling current. The practical application of the model is demonstrated by the example of mathematical processing of the LTCVCs of HOPG surface containing different structural defects.

scholarly journals Влияние контактной разности потенциалов на вольт-амперные характеристики в сканирующей туннельной спектроскопии

2021 ◽  
Vol 91 (11) ◽  
pp. 1769
Author(s):  
М.В. Кузьмин ◽  
М.А. Митцев
Keyword(s):  
Contact Potential Difference ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Differential Conductivity ◽  
Contact Potential ◽  
Potential Barriers ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Work Functions ◽  
Conductivity Spectra

Using the energy diagrams of asymmetric potential barriers formed at the contact of two metals with different work functions, the influence of contact potential difference on the current-voltage characteristics and differential conductivity spectra measured by scanning tunneling spectroscopy is considered. It is shown that the obtained conclusions are in qualitative agreement with the experimental results for ytterbium nanofilms with the thickness of 16 monolayers (6.08 nm). However, they significantly differ quantitatively. The analysis of such diffrences is performed.

Molecular-Scale Structure of Pentacene Interfaces with Si (111)

2006 ◽  
Vol 965 ◽  
Author(s):  
Soonjoo Seo ◽  
Paul G. Evans
Keyword(s):  
Scanning Tunneling Spectroscopy ◽  
Structural Defects ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Semiconductor Thin Films ◽  
Disordered Layer ◽  
Temperature Scanning ◽  
Molecular Layers ◽  
Preparation Techniques ◽  
Imaging Conditions

ABSTRACTThe morphology and crystal structure of the first few molecular layers of organic semiconductor thin films at organic-inorganic interfaces are important from both electronic and structural perspectives. The first upright layer of pentacene on Si (111) forms on top of a disordered layer of strongly bonded pentacene molecules in a structure similar to the pentacene monolayers formed on insulators. We describe a high-resolution structural study of this crystalline phase of pentacene using low-temperature scanning tunneling microscopy (STM). The arrangement of molecules in these layers observed with STM agrees the results of with structural studies using scattering techniques. The imaging conditions and sample preparation techniques necessary to achieve molecular resolution can be adapted to subsequent STM and scanning tunneling spectroscopy experiments probing individual structural defects including vacancies, dislocations and grain boundaries within and between islands.

CURRENT–VOLTAGE PROPERTIES OF SELF-ASSEMBLY MONOLAYERS ON AU(111) SUBSTRATE USING SCANNING TUNNELING MICROSCOPY

2006 ◽  
Vol 05 (06) ◽  
pp. 907-911
Author(s):  
NAM-SUK LEE ◽  
HOON-KYU SHIN ◽  
YOUNG-SOO KWON
Keyword(s):  
Thin Film ◽  
Electrical Properties ◽  
Scanning Tunneling Microscopy ◽  
Self Assembly ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Organic Thin Film ◽  
Tunneling Microscopy ◽  
Current Voltage ◽  
Self Assembled

This study observes the morphology of self-assembled organic thin film that is formed at room temperature using a Scanning Tunneling Microscopy (STM) and examines its electrical properties using a Scanning Tunneling Spectroscopy (STS). The specimen used in this experiment that has a functional group for both sides and will be controlled to make self-assembled onto the Au (111) substrate. After the dilution of the specimen by 1 mM/ml and self-assembled onto the Au (111) substrate. Using a STM, the images of organic thin film can be observed. In addition, the electrical properties of organic thin film can also be examined by the junction structure of STM–organic thin film– Au (111) substrate by using a STM tip. As a result, we measured current–voltage (I–V) curve using STS, I–V curve also clearly shows several current peaks between the negative bias region (-1.42 V) and the positive bias region (1.30 V), respectively.

Scanning Tunneling Microscopy Imaging and Spectroscopy of a Single Viologen Molecule

2008 ◽  
Vol 8 (9) ◽  
pp. 4621-4625
Author(s):  
Nam-Suk Lee ◽  
Chang-Heon Yang ◽  
Won-Suk Choi ◽  
Young-Soo Kwon
Keyword(s):  
Self Assembly ◽  
Current Mode ◽  
Scanning Tunneling Spectroscopy ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Microscopy Imaging ◽  
Current Voltage ◽  
Imaging And Spectroscopy ◽  
Stm Images

A low-temperature ultrahigh-vacuum scanning tunneling microscope (UHV-STM) was used to image viologen (N-methyl-N′-di (8-mercaptooctyl)-4,4′-bipyridinium; HSC8VC8SH) molecules and to perform local spectroscopic measurements on these molecules. Self-assembly of viologen molecules was conducted on Au (111), which had been thermally deposited onto freshly cleaved, heated mica. Here, we demonstrate a novel SAM matrix appropriate for the isolation of viologen molecules composed of octanethiol (C8) in which HSC8VC8SH was inserted at defects in the molecular lattice. The isolated single molecules of viologen inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. STM images at 298 K showed protrusions with a topographic height of about 2.71 nm (HSC8VC8SH) with viologen molecules that self-assembled on the substrate. The current–voltage (I–V) characteristics were measured while the electrical properties of the formed monolayer were scanned using scanning tunneling spectroscopy (STS). We found the high peak current-like rectification at +1.14 V (HSC8VC8SH). The rectification ratios, RR = J (at +2.5 V)/J (at −2.5 V), are in the range of 4.47.

scholarly journals Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 224
Author(s):  
Kalyan Biswas ◽  
Lin Yang ◽  
Ji Ma ◽  
Ana Sánchez-Grande ◽  
Qifan Chen ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Open Shell ◽  
Scanning Tunneling Spectroscopy ◽  
Membered Ring ◽  
Structural Defects ◽  
Scanning Tunneling ◽  
Honeycomb Lattice ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force

The synthesis of nanographenes (NGs) with open-shell ground states have recently attained increasing attention in view of their interesting physicochemical properties and great prospects in manifold applications as suitable materials within the rising field of carbon-based magnetism. A potential route to induce magnetism in NGs is the introduction of structural defects, for instance non-benzenoid rings, in their honeycomb lattice. Here, we report the on-surface synthesis of three open-shell non-benzenoid NGs (A1, A2 and A3) on the Au(111) surface. A1 and A2 contain two five- and one seven-membered rings within their benzenoid backbone, while A3 incorporates one five-membered ring. Their structures and electronic properties have been investigated by means of scanning tunneling microscopy, noncontact atomic force microscopy and scanning tunneling spectroscopy complemented with theoretical calculations. Our results provide access to open-shell NGs with a combination of non-benzenoid topologies previously precluded by conventional synthetic procedures.

Scanning tunneling spectroscopy of carbon nanotubes

1994 ◽  
Vol 9 (2) ◽  
pp. 259-262 ◽  
Author(s):  
Charles H. Olk ◽  
Joseph P. Heremans
Keyword(s):  
Carbon Nanotubes ◽  
Scanning Tunneling Microscopy ◽  
Experimental Evidence ◽  
Density Of States ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
One Dimensional ◽  
Current Voltage ◽  
Show Evidence

Calculations predict that carbon nanotubes may exist as either semimetals or semiconductors, depending on diameter and degree of helicity. This communication presents experimental evidence supporting the calculations. Scanning tunneling microscopy and spectroscopy (STM-S) data taken in air on nanotubes with outer diameters from 17 to 90 Å show evidence of one-dimensional behavior; the current-voltage (I-V) characteristics are consistent with a density of states containing Van Hove type singularities for which the energies vary linearly with inverse nanotube diameter.

INFLUENCE OF A TIP/SAMPLE INTERACTION ON SCANNING TUNNELING SPECTROSCOPY DATA

1995 ◽  
Vol 02 (02) ◽  
pp. 219-223 ◽  
Author(s):  
V.G. ZAVODINSKY ◽  
I.A. KUYANOV
Keyword(s):  
Electronic Structure ◽  
Local Density ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Local Density Of States ◽  
Tunnel Current ◽  
Free Sample ◽  
Discrete Variational Method ◽  
Local Electronic Structure ◽  
Sample Distance

The electronic states and the tunnel current for the W/Si and W/Al tip/sample systems were calculated by the first-principles discrete-variational method of the local-density approximation. It was found that the local-electronic structure of the Si surface resembles that of a free sample even for the tip/sample distances of 2–3 Å. The electronic structure of the Al surface is more sensitive to the tip/sample interaction and approaches the free surface form when the tip/sample distance is larger than 4 Å. The local density of states of the W tip also depends on the tip/sample distance and must be taken into account in the tunnel-current calculations and in the interpretations of the STS data.

Microscopy of Metal Oxide Surfaces

2000 ◽  
Vol 6 (4) ◽  
pp. 324-328
Author(s):  
Martin R. Castell ◽  
Sergei L. Dudarev ◽  
Christiane Muggelberg ◽  
Adrian P. Sutton ◽  
G. Andrew D. Briggs ◽  
...  
Keyword(s):  
Surface Structure ◽  
Room Temperature ◽  
Low Voltage ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metal Oxide Surfaces ◽  
Electrically Conducting ◽  
Temperature Scanning ◽  
Electronic Surface ◽  
Voltage Scanning

Abstract Elevated temperature scanning tunneling microscopy is used to study oxides that are room temperature insulators but become sufficiently electrically conducting at higher temperatures to allow imaging to be performed. Atomic resolution images of NiO, CoO, and UO2 have been obtained in this fashion which allow surface structure and defect determination. To complement the experiments, modeling of the electronic surface structure reveals which atomic sites give rise to the contrast observed in the images. Low voltage scanning electron microscopy is used to image small equilibrium pores in UO2 single crystals to evaluate the surface energy ratio of the (111) to (001) surfaces.

Microscopy of Metal Oxide Surfaces

2000 ◽  
Vol 6 (4) ◽  
pp. 324-328 ◽  
Author(s):  
Martin R. Castell ◽  
Sergei L. Dudarev ◽  
Christiane Muggelberg ◽  
Adrian P. Sutton ◽  
G. Andrew D. Briggs ◽  
...  
Keyword(s):  
Surface Structure ◽  
Room Temperature ◽  
Low Voltage ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metal Oxide Surfaces ◽  
Electrically Conducting ◽  
Temperature Scanning ◽  
Electronic Surface ◽  
Voltage Scanning

AbstractElevated temperature scanning tunneling microscopy is used to study oxides that are room temperature insulators but become sufficiently electrically conducting at higher temperatures to allow imaging to be performed. Atomic resolution images of NiO, CoO, and UO2 have been obtained in this fashion which allow surface structure and defect determination. To complement the experiments, modeling of the electronic surface structure reveals which atomic sites give rise to the contrast observed in the images. Low voltage scanning electron microscopy is used to image small equilibrium pores in UO2 single crystals to evaluate the surface energy ratio of the (111) to (001) surfaces.

SCANNING TUNNELING SPECTROSCOPY ON THE GdSr2RuCu2O8 COMPOUND

2003 ◽  
Vol 17 (04n06) ◽  
pp. 608-613 ◽  
Author(s):  
F. BOBBA ◽  
F. GIUBILEO ◽  
M. GOMBOS ◽  
C. NOCE ◽  
A. VECCHIONE ◽  
...  
Keyword(s):  
Coulomb Blockade ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Conductance ◽  
Zero Bias ◽  
Voltage Range ◽  
Current Voltage ◽  
Spectroscopic Information ◽  
Current Voltage Characteristics

Topographic and spectroscopic information on GdSr2RuCu2O8 sintered pellets have been obtained by a home built low temperature Scanning Tunneling Microscope (STM) operating at 4.2 K. The topographic image of the surface showed non homogeneous samples with grains of typical size of about 100 nm. In many locations studied, the Tunneling Spectroscopy reveals the presence of charging effects in the current-voltage characteristics over a voltage range up to 100 mV. Two types of charging effects are clearly distinguished: one corresponds to the reduction of the tunneling conductance around zero bias and is attributed to the Coulomb blockade, and another onw, a stepwise increasing of the current as a function of the bias voltage is identified as Coulomb staircase regime. Besides these spurious charging effects, the current-voltage characteristics often show a pronounced non-linearity around 4.0 mV. This non-linearity, disappearing above the critical temperature of the materials, is connected to the superconducting gap in the GdSr 2 RuCu 2 O 8.

Sign in / Sign up

Export Citation Format

Share Document