Two Dimensional Imaging of the Laterally Inhomogeneous Au/4H-SiC Schottky Barrier by Conductive Atomic Force Microscopy

2007 ◽  
Vol 556-557 ◽  
pp. 545-548 ◽  
Author(s):  
Filippo Giannazzo ◽  
Fabrizio Roccaforte ◽  
S.F. Liotta ◽  
Vito Raineri

We present a novel approach based on conductive atomic force microscopy (c-AFM) for nano-scale mapping of the Schottky barrier height (SBH) between a semiconductor and an ultrathin (1-5 nm) metal film. The method was applied to characterize the uniformity of the Au/4H-SiC Schottky contact, which is attractive for applications due to the high reported (∼1.8 eV) SBH value. Since this system is very sensitive to the SiC surface preparation, we investigated the effect on the nano-scale SBH distribution of a ∼2 nm thick not uniform SiO2 layer. The macroscopic I-V characteristics on Au/SiC and Au/not uniform SiO2/SiC diodes showed that the interfacial oxide lowers the average SBH. The c-AFM investigation is carried out collecting arrays of I-V curves for different tip positions on 1μm×1μm area. From these curves, 2D SBH maps are obtained with 10- 20 nm spatial resolution and energy resolution <0.1 eV. The laterally inhomogeneous character of the Au/SiC contact is demonstrated. In fact, a SBH distribution peaked at 1.8 eV and with tails from 1.6 eV to 2.1 eV is obtained. Moreover, in the presence of the not uniform oxide at the interface, the SBH distribution exhibits a 0.3 eV peak lowering and a broadening (tails from 1.1 eV to 2.1 eV).

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
F. Ruffino ◽  
A. Canino ◽  
M. G. Grimaldi ◽  
F. Giannazzo ◽  
F. Roccaforte ◽  
...  

A bottom-up methodology to fabricate a nanostructured material by Au nanoclusters on 6H-SiC surface is illustrated. Furthermore, a methodology to control its structural properties by thermal-induced self-organization of the Au nanoclusters is demonstrated. To this aim, the self-organization kinetic mechanisms of Au nanoclusters on SiC surface were experimentally studied by scanning electron microscopy, atomic force microscopy, Rutherford backscattering spectrometry and theoretically modelled by a ripening process. The fabricated nanostructured materials were used to probe, by local conductive atomic force microscopy analyses, the electrical properties of nano-Schottky contact Au nanocluster/SiC. Strong efforts were dedicated to correlate the structural and electrical characteristics: the main observation was the Schottky barrier height dependence of the nano-Schottky contact on the cluster size. Such behavior was interpreted considering the physics of few electron quantum dots merged with the concepts of ballistic transport and thermoionic emission finding a satisfying agreement between the theoretical prediction and the experimental data. The fabricated Au nanocluster/SiC nanocontact is suggested as a prototype of nano-Schottky diode integrable in complex nanoelectronic circuits.


Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 803 ◽  
Author(s):  
Filippo Giannazzo ◽  
Emanuela Schilirò ◽  
Giuseppe Greco ◽  
Fabrizio Roccaforte

Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1–xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.


2015 ◽  
Vol 821-823 ◽  
pp. 424-427
Author(s):  
Marilena Vivona ◽  
Filippo Giannazzo ◽  
Kassem Alassaad ◽  
Véronique Soulière ◽  
Gabriel Ferro ◽  
...  

This work reports on the morphological and electrical characteristics of Ni/4H-SiC Schottky contacts, fabricated on epitaxial layers intentionally covered by micrometric size Ge-droplets. Specifically, the Ge-droplets behave as preferential paths for the vertical current conduction, as observed at nanometric scale by conductive atomic force microscopy. As a consequence, the electrical I-V characteristics of these Ni contacts revealed the presence of a double-barrier, thus indicating an inhomogeneity in the interface. This behavior was associated to the local Schottky barrier lowering contribution due to the Ge-presence. These results can be useful to explore the possibility of controlling the contact (Schottky or Ohmic) properties by changing the size and the distribution of the surface impurities.


2010 ◽  
Vol 25 (2) ◽  
pp. 213-218 ◽  
Author(s):  
Shengde Liang ◽  
Brian A. Ashcroft

We used conductive-atomic force microscopy (c-AFM) for electrical characterization of self-assembled epitaxial iron silicide nanowires (NWs) on Si (110). The NWs, 6 nm high by 10 nm wide and several micrometers long, were partially covered by a macro-gold-pad as one electrode. Another electrode is the conductive AFM tip. The resistance of a single FeSi2 NW was measured to be 29.7 kΩ, corresponding to a resistivity of 150 ± 30 μΩ·cm. A Schottky barrier formed between NWs and silicon substrate was clearly demonstrated, which offers electrical isolation for NWs. An equivalent circuit model based on the Schottky barrier was proposed and was correlated with measurement results. This simple electrical characterization approach may find wide applications for various one-dimensional nanostructures.


2016 ◽  
Vol 858 ◽  
pp. 1137-1140 ◽  
Author(s):  
Gabriele Fisichella ◽  
Giuseppe Greco ◽  
Salvatore di Franco ◽  
Raffaella Lo Nigro ◽  
Emanuela Schilirò ◽  
...  

This paper presents a study of the vertical current transport in a graphene (Gr) heterostructure with AlxGa1-xN/GaN, which represent the main building block of a novel high frequency device, the hot electron transistor (HET) with Gr base. The morphological and electrical properties of this heterostructures have been investigated at nanoscale by atomic force microscopy (AFM) and conductive atomic force microscopy (CAFM). In particular, local current-voltage measurements by the CAFM probe revealed the formation of a Schottky contact with low barrier height (∼0.41 eV) and excellent lateral uniformity between Gr and AlGaN. Basing on the electrical parameters extracted from this characterization, the theoretical performances of a HET formed by a metal/Al2O3/Gr/AlGaN/GaN stack have been evaluated.


2015 ◽  
Vol 1109 ◽  
pp. 238-242 ◽  
Author(s):  
R. Muhammad ◽  
Yussof Wahab ◽  
Zulkafli Othaman ◽  
Samsudi Sakrani

Utilizing semiconductor nanowires for optoelectronics device requires exact knowledge of their current-voltage properties. In this report, we examine accurate on-top imaging and I-V characterization of individual vertical Gallium Arsenide Nanowires (GaAs NWs) using conductive atomic force microscopy without additional microscopy tools, thus allowing versatile application. The measured current-voltage characteristic of a single NW shows the typical performance of a Schottky contact, which caused by the contact between the metallic AFM tip and the top of NWs. The height of the Schottky barrier is dependent on the diameter of the nanowires. The linear part of the curve was used to calculate the differential resistance, which was found to be about 25 to 100 MΩ. Energy band gap for GaAs NW was found to be 1.5 eV by differential conductivity measurement.


Author(s):  
Lucile C. Teague Sheridan ◽  
Linda Conohan ◽  
Chong Khiam Oh

Abstract Atomic force microscopy (AFM) methods have provided a wealth of knowledge into the topographic, electrical, mechanical, magnetic, and electrochemical properties of surfaces and materials at the micro- and nanoscale over the last several decades. More specifically, the application of conductive AFM (CAFM) techniques for failure analysis can provide a simultaneous view of the conductivity and topographic properties of the patterned features. As CMOS technology progresses to smaller and smaller devices, the benefits of CAFM techniques have become apparent [1-3]. Herein, we review several cases in which CAFM has been utilized as a fault-isolation technique to detect middle of line (MOL) and front end of line (FEOL) buried defects in 20nm technologies and beyond.


Author(s):  
Jon C. Lee ◽  
J. H. Chuang

Abstract As integrated circuits (IC) have become more complicated with device features shrinking into the deep sub-micron range, so the challenge of defect isolation has become more difficult. Many failure analysis (FA) techniques using optical/electron beam and scanning probe microscopy (SPM) have been developed to improve the capability of defect isolation. SPM provides topographic imaging coupled with a variety of material characterization information such as thermal, magnetic, electric, capacitance, resistance and current with nano-meter scale resolution. Conductive atomic force microscopy (C-AFM) has been widely used for electrical characterization of dielectric film and gate oxide integrity (GOI). In this work, C-AFM has been successfully employed to isolate defects in the contact level and to discriminate various contact types. The current mapping of C-AFM has the potential to identify micro-leaky contacts better than voltage contrast (VC) imaging in SEM. It also provides I/V information that is helpful to diagnose the failure mechanism by comparing I/V curves of different contact types. C-AFM is able to localize faulty contacts with pico-amp current range and to characterize failure with nano-meter scale lateral resolution. C-AFM should become an important technique for IC fault localization. FA examples of this technique will be discussed in the article.


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