Exponential behavior of the Ohmic transport in organic films

Colesniuc, Corneliu N.; Biswas, Rudro R.; Hevia, Samuel A.; Balatsky, Alexander V.; Schuller, Iván K.

doi:10.1103/physrevb.83.085414

Cited by 14 publications

(13 citation statements)

References 26 publications

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“…For the interpretation of this linear dependence, we follow a simple multistep tunnelling model. [ 22 ] In this model the electrons are injected from the metal through an interface barrier into the fi rst molecular layer, and then they undergo a number of tunnelling steps from molecule to molecule until they reach the second electrode. Hence, the probability of an electron crossing the whole molecular layer will be the product of the probabilities of each tunnelling event:…”

Section: Doi: 101002/adma201004672mentioning

confidence: 99%

Room‐Temperature Spin Transport in C₆₀‐Based Spin Valves

et al. 2011

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Spintronics, or the possibility of performing electronics with the spin of the electron, has been fundamental for the exponential growth of digital data storage which has occurred in the last decades. Indeed, hard-disk drives read-heads are the maximum exponent of what is currently being called fi rstgeneration spintronic devices. Current read-heads, although technologically very complex, are scientifi cally based simply on the tunnel magnetoresistance effect (TMR; magnetoresistance being the change in electrical resistance of a device under the application of an external magnetic fi eld). A tunnel magnetoresistive vertical spin valve is composed of two ferromagnetic layers separated by a thin (around 1 nm) insulating layer, and the resistance of the structure can be switched between two different values upon the application of a magnetic fi eld capable of rotating the magnetization vector of the ferromagnetic layers from parallel to antiparallel. [ 1 ] For the eventual success of a second-generation of spintronic devices, more complex mechanisms than the nanometre-distance spin transport in metallic or insulating materials have to be obtained. In particular, coherent spin transport at distances above a few nm and spin manipulation are unavoidable requirements for the production of sophisticated prototypes of, for example, spin transistors or spin light-emitting diodes. [ 2 , 3 ] Organic semiconductors (OS) have emerged as promising materials for advanced spintronics applications. Their spin relaxation mechanisms, mainly represented by spin orbit interaction and hyperfi ne interaction with protons, [ 4 ] are very small, and long spin lifetimes have been consistently detected. [ 5 ] Moreover, in spite of the relatively low carrier mobility of these materials, organic vertical spin valves with semiconducting channels thicker than 100 nm have been demonstrated. [6][7][8][9][10][11] In parallel, OS ultrathin layers perform successfully as spin tunnel junctions, and extremely high ( > 300%) magnetoresistance (MR) values have been obtained at low temperatures. [ 12 ] Regarding possible applications of spin transport in OS, a basic operational requirement is the room temperature (RT) operation of the devices. So far, only organic spin tunnel junctions have shown any signifi cant MR effect at RT. [13][14][15][16][17] By contrast, most devices employing thicker organic layer ( > 15 nm) show a clear decay of the MR well below RT. [ 6-11 , 18 ] In this work, we present signifi cant RT MR values (in excess of 5%) on C 60 -based vertical spin valves for different thickness of the C 60 interlayer (from 5 nm to 28 nm) up to high applied biases ( ∼ 1 V), demonstrating coherent spin transport through C 60 molecules. We also show that transport of spin-polarized electrons is in agreement with a multi-step tunnelling regime.C 60 , the fi rst discovered fullerene, was chosen considering its several properties that make it ideal for organic spintronic devices. Firstly, C 60 molecules can be sublimated in ultra-high vacuum (UHV) a...

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Section: Doi: 101002/adma201004672mentioning

confidence: 99%

Room‐Temperature Spin Transport in C₆₀‐Based Spin Valves

et al. 2011

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“…III B. Approximating the number of hops N by l and the average coordination number C by ρ, we arrive at Eq. (35). (We assume that N is large and ignore its fractional part in this heuristic derivation.)…”

Section: A Toy Modelmentioning

confidence: 99%

Hopping transport in systems of finite thickness or length

Родин

Fogler

2011

Phys. Rev. B

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Variable-range hopping transport along short one-dimensional wires and across the shortest dimension of thin three-dimensional films and narrow two-dimensional ribbons is studied theoretically. Geometric and transport characteristics of the hopping resistor network are shown to depend on temperature T and the dimensionality of the system. In two and three dimensions the usual Mott law applies at high T where the correlation length of the network is smaller than the sample thickness. As T decreases, the network breaks into sparse filamentary paths, while the Mott law changes to a different T-dependence, which is derived using the percolation theory methods. In one dimension, deviations from the Mott law are known to exist at all temperatures because of rare fluctuations. The evolution of such fluctuations from highly-resistive "breaks" at high T to highly-conducting "shorts" at low T is elucidated.Comment: 10 pages, 8 figure

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“…Determination of these parameters in those compounds plays an important role in decisions about the suitability of the material for a particular device application. The dc electrical properties of devices using various mono Pc thin film sandwich devices have been extensively studied in recent years, 78,79 but relatively little work has been done on the dc behavior of ball-type Pcs.…”

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confidence: 99%