Transport localization in heterogeneous Schottky barriers of quantum-defined metal films

Giannazzo, Filippo; Roccaforte, Fabrizio; Raineri, V.; Liotta, S.F.

doi:10.1209/epl/i2006-10018-8

Cited by 49 publications

(32 citation statements)

References 15 publications

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“…C-V analysis considers an average SBH value (Φ CV ) over the whole interface, therefore this value is very likely to be closer to Φ 0 9,15 . Ballistic electron emission microscopy on Pd/6H-SiC barriers, has recently confirmed the presence of a nanometer scale distribution of SBH 19 , whilst conductive atomic force microscopy has also been used to map inhomogeneities on Au/4H-SiC samples 20 . The origins of inhomogeneous Schottky barrier theory dates back to the 1960's when non-linearities within the classic Richardson plot hindered the extraction of the SBH and Richardson constant (A * * ).…”

Section: Introductionmentioning

confidence: 99%

Analysis of inhomogeneous Ge/SiC heterojunction diodes

Gammon

Pérez‐Tomás

Shah

et al. 2009

Journal of Applied Physics

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In this article Schottky barrier diodes comprising of a n-n Germanium-Silicon Carbide (Ge-SiC) heterojunction are electrically characterised. Circular transmission line measurements prove that the nickel front and back contacts are ohmic, isolating the Ge/SiC heterojunction as the only contributor to the Schottky behaviour. Current-voltage plots taken at varying temperature (IVT) reveal that the ideality factor (n) and Schottky barrier height (Φ) are temperature dependent and that incorrect values of the Richardson constant (A * * ) are being produced, suggesting an inhomogeneous barrier. Techniques originally designed for metal-semiconductor SBH extraction are applied to the heterojunction results to extract values of Φ and A * * that are independent of temperature. The experimental IVT data is replicated using the Tung model. It is proposed that small areas, or patches, making up only 3% of the total contact area will dominate the I-V results due to their low SBH of 1.033 eV. The experimental IVT data is also analysed statistically using the extracted values of Φ to build up a Gaussian distribution of barrier heights, including the standard deviation and a mean SBH of 1.126 eV, which should be analogous to the SBH extracted from capacitance-voltage (C-V) measurements. Both techniques yield accurate values of A * * for SiC. However, the C-V analysis did not correlate with the mean SBH as expected.

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Section: Introductionmentioning

confidence: 99%

Analysis of inhomogeneous Ge/SiC heterojunction diodes

Gammon

Pérez‐Tomás

Shah

et al. 2009

Journal of Applied Physics

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“…In this way, TRCAFM combines the high resolution of dynamic scanning probe microscopy in morphological mapping and the ability of nanoscale resolution current mapping of CAFM. 16 In the last years, CAFM has been applied to probe electronic transport through various laterally inhomogeneous metal/semiconductor systems, including Au/SiC, 18 Pt/GaN, 19 epitaxial graphene/SiC(0001). 16 For thin enough metal films compared with the tip contact radius, a lateral resolution comparable to the tip size has been demonstrated.…”

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confidence: 99%

Nanoscale study of the current transport through transrotational NiSi/n-Si contacts by conductive atomic force microscopy

Alberti

Giannazzo

2012

Applied Physics Letters

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The average electrical behaviour of transrotational NiSi layers used as contacts in diode structures on n-type Si was correlated to the local structure and conduction paths inside each domain by using conductive-atomic force microscopy. It was found that, independently of the domain orientation, the central portion of the domain (core $ 20 nm) possesses a Schottky barrier lower than in the rest of the structure. This was ascribed to an effect of the structural coupling between the NiSi lattice and the silicon substrate as realised at the interface in virtue of the pseudoepitaxial relationship established since the early stages of the reaction. V C 2012 American Institute of Physics.It is well assessed that the use of nickel silicide on source and drain contacts of microelectronic devices has a significant impact to reduce series and contact resistances. 1,2 The drastic scaling down of devices and also the recent interest to use plastic substrates, which have low critical temperatures (e.g., Tc polyimide 200 C), pose more and more the need to optimize the material properties, and particularly, the interfaces quality on the nanoscale. It is thus mandatory to know in more detail the process of silicide formation since the very early stages of the reaction process to control the structure and the stoichiometry of the silicide, especially on very thin layers.The pioneering studies on the very early stages of Ni-Si reaction date from 1980. It was observed that, on a perfectly cleaned Si surface, a Ni-Si precursor layer is formed even at room temperature (RT) after deposition of a very thin nickel layer (<2 nm). 3 The precursor layer (or diffusion layer) is formed once nickel atoms come in contact with silicon, and reasonably maintained also after subsequent reaction: its presence is thus adduced as the reason why all the Ni-silicide phases have comparable Schottky barrier height (e.g., 0.66 eV on n-type Si). 4 The precursor layer has a disordered structure with Ni atoms having the short range environment similar to that encountered in the NiSi 2 lattice 3 and originates from the diffusion process of Ni atoms into the Si lattice by means of tetrahedral interstitial sites. Due to the similarity of the diffusion layer structure to that of the NiSi 2 lattice, an epitaxial silicide layer is formed upsetting the usual sequence of phases encountered in thick layers, without significant transport of matter, 3 by annealing at relatively low temperature ($450 C). A different scenario is instead observed by depositing at RT a supply of Ni atoms on top of the interfacial diffusion layer. When a supply of Ni is then present, the role of the diffusion layer, as precursor to the reaction process, is shadowed by the fast diffusion of nickel atoms, and a conventional phase sequence is observed with NiSi 2 formed at the end, at the NiSi-Si interface. 1 We have recently 5 shown that the direct transition to NiSi 2 can be assured even in the presence of a nickel supply ($7 nm) by using a $2 nm-thick precursor layer and by reducing anneali...

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“…Lately, an alternative approach based on conductive atomic force microscopy (C-AFM) was demonstrated [62], which overcomes some of the BEEM limitations. Scanning a forward biased C-AFM tip in contact on an ultrathin (< 5 nm) metal film, current flows only through a very localized region (in the order of the tip diameter) of the macroscopic metal-semiconductor contact, i.e., a "nano-Schottky diode" is formed point by point.…”

Section: Discussionmentioning

confidence: 99%

“…Giannazzo et al [62] investigated the nanoscale homogeneity of the Schottky barrier in a Au/6H-SiC structure, with and without the presence of a nanometric non-uniform interfacial thermal oxide layer, i.e., a typical situation that may occur during device fabrication. A method based on conductive atomic force microscopy (C-AFM) was used for the local mapping of the barrier uniformity with a spatial resolution in the order of the AFM tip size [62] (see appendix A.1).…”

Section: Introductionmentioning

confidence: 99%

Nanoscale transport properties at silicon carbide interfaces

Roccaforte¹,

Giannazzo²,

Raineri³

2010

J. Phys. D: Appl. Phys.

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Abstract. Wide band gap semiconductors promise devices with performances not achievable using silicon technology. Among them, Silicon Carbide (SiC) is considered the top-notch material for a new generation of power electronic devices, ensuring the improved energy efficiency requested in the modern society. In spite of the significant progresses achieved in the last decade in the material quality, there are still several scientific open issues related to the basic transport properties at SiC interfaces and ion-doped regions that can affect the devices performances, keeping them still far from their theoretical limits. Hence, significant efforts in fundamental research at nanoscale have become mandatory to better understand the carrier transport phenomena, both at surfaces and interfaces. In this paper, the most recent experiences on nanoscale transport properties will be addressed, reviewing the relevant key points for the basic devices building blocks. The selected topics include the major concerns related to the electronic transport in metal/SiC interfaces, to the carrier concentration and mobility in ion-doped regions, and to channel mobility in metal/oxide/SiC systems. Some aspects related to interfaces between different SiC polytypes are also presented. All these issues will be discussed considering the current status and the drawbacks of SiC devices.

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Transport localization in heterogeneous Schottky barriers of quantum-defined metal films

Cited by 49 publications

References 15 publications

Analysis of inhomogeneous Ge/SiC heterojunction diodes

Analysis of inhomogeneous Ge/SiC heterojunction diodes

Nanoscale study of the current transport through transrotational NiSi/n-Si contacts by conductive atomic force microscopy

Nanoscale transport properties at silicon carbide interfaces

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