Atomic force microscope-assisted scanning tunneling spectroscopy under ambient conditions

The morphology and conductivity of indium/tin oxide (ITO) film have a large impact on the performance of light emitting diode (LED) devices using ITO as an anode. Atomic Force Microscope and current image tunneling spectroscopy (CITS) were used to probe the surface morphology and scanning tunneling spectroscopy (STS) of ITO surface. The morphology of all ITO films studied revealed a spherical aggregation with various grain sizes of 20~50 nm, depends on clean methods. It was also found that the conductivity of ITO films is related to film thickness. In general, thicker film shows higher conductivity. Nevertheless, the conductivity within a single grain is very homogeneous. On the other hand, the topographies of poly(N-(4-sulfophenyl)aniline (PSA) films revealed a rod-shaped aggregation with a diameter of 50 nm. The corresponding CITS images revealed conducting islands with irregular shape and size. The conductivity within a single polymer rod is not homogeneous.

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Local Electric Property Modification of Ferroelectric Tunnel Junctions Induced by Variation of Polarization Charge Screening Conditions under Measurement with Scanning Probe Techniques

Nanomaterials ◽

10.3390/nano11123323 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3323

Author(s):

Natalia Andreeva ◽

Anatoliy Petukhov ◽

Oleg Vilkov ◽

Adrian Petraru ◽

Victor Luchinin

Keyword(s):

Tunnel Junctions ◽

Scanning Tunneling Spectroscopy ◽

Scanning Probe ◽

Scanning Tunneling ◽

Tunnel Barrier ◽

Ambient Conditions ◽

Conductive Atomic Force Microscopy ◽

Force Microscopy ◽

Atomic Force ◽

The Difference

Scanning tunneling spectroscopy in ultrahigh vacuum conditions and conductive atomic-force microscopy in ambient conditions were used to study local electroresistive properties of ferroelectric tunnel junctions SrTiO3/La0.7Sr0.3MnO3/BaTiO3. Interestingly, experimental current-voltage characteristics appear to strongly depend on the measurement technique applied. It was found that screening conditions of the polarization charges at the interface with a top electrode differ for two scanning probe techniques. As a result, asymmetry of the tunnel barrier height for the opposite ferroelectric polarization orientations may be influenced by the method applied to study the local tunnel electroresistance. Our observations are well described by the theory of electroresistance in ferroelectric tunnel junctions. Based on this, we reveal the main factors that influence the polarization-driven local resistive properties of the device under study. Additionally, we propose an approach to enhance asymmetry of ferroelectric tunnel junctions during measurement. While keeping the high locality of scanning probe techniques, it helps to increase the difference in the value of tunnel electroresistance for the opposite polarization orientations.

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The atomic-force microscope and its future in biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149350 ◽

1993 ◽

Vol 51 ◽

pp. 704-705

Author(s):

Jean-Paul Revel

Keyword(s):

Silicon Nitride ◽

Laser Beam ◽

Atomic Force Microscope ◽

Scanning Tunneling Microscope ◽

Point Of View ◽

Scanning Tunneling ◽

Close Relative ◽

Tunneling Microscope ◽

Atomic Force ◽

Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

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Scanning-tunneling spectroscopy on conjugated polymer films

MRS Proceedings ◽

10.1557/proc-771-l4.3 ◽

2003 ◽

Vol 771 ◽

Author(s):

M. Kemerink ◽

S.F. Alvarado ◽

P.M. Koenraad ◽

R.A.J. Janssen ◽

H.W.M. Salemink ◽

...

Keyword(s):

Polymer Films ◽

Conjugated Polymer ◽

Three Dimensional ◽

Field Enhancement ◽

Direct Consequence ◽

Scanning Tunneling Spectroscopy ◽

Tunneling Spectroscopy ◽

Band Alignment ◽

Scanning Tunneling ◽

Order Of Magnitude

AbstractScanning-tunneling spectroscopy experiments have been performed on conjugated polymer films and have been compared to a three-dimensional numerical model for charge injection and transport. It is found that field enhancement near the tip apex leads to significant changes in the injected current, which can amount to more than an order of magnitude, and can even change the polarity of the dominant charge carrier. As a direct consequence, the single-particle band gap and band alignment of the organic material can be directly obtained from tip height-voltage (z-V) curves, provided that the tip has a sufficiently sharp apex.

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