Mn5Ge3C0.6/Ge(111) Schottky contacts tuned by a n-type ultra-shallow doping layer

International audienceMn 5 Ge 3 Cxcompound is of great interest for spintronics applications. 10 The various parameters of Au/Mn 5 Ge 3 C 0.6 /Ge(111) and Au/Mn 5 Ge 3 C 0.6 /δ-doped Ge(111) Schottky diodes were measured in the temperature range of 30-300 K by using current-voltage and capacitance-voltage techniques. The Schottky barrier heights and ideality factors were found to be temperature dependent. These anomaly behaviours were explained by Schottky barriers inhomogeneities 15 and interpreted by means of Gaussian distributions model of the Schottky barrier heights. Following this approach we show that the Mn 5 Ge 3 C 0.6 /Ge contact is described with a single Gaussian distribution and a conduction mechanism mainly based on the thermoionic emission. On the other hand the Mn 5 Ge 3 C 0.6 /δ-doped Ge contact is depicted with two Gaussian distributions according to the 20 temperature and a thermionic-field emission process. The differences between the two types of contacts are discussed according to the distinctive features of the growth of heavily doped germanium thin films

Growth and structural characterization of molecular superlattice of quaterrylene and N,N′-dioctyl-3,4,9,10-perylenedicarboximide

A molecular superlattice consisting of alternate layers of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) and quaterrylene was prepared by using an ultra-slow deposition technique. Film growth under equilibrium conditions with precise optimization of the substrate temperature enabled the layer-by-layer stacking of hetero-molecules at a single-layer level. The morphology of the films and the orientation of the molecules in each layer were analyzed by atomic force microscopy (AFM) and an X-ray reflection (XRR) technique

Early Stage of Growth of a Perylene Diimide Derivative Thin Film Growth on Various Si(001) Substrates

International audienceThis study deals with the growth mode of N,N’-dipenthyl-3,4,9,10-perylenetetracarboxylic diimide(PTCDI-5C) thin films from less than one monolayer to 23 monolayers thick. The effects of growthtemperature and the thickness and nature of the substrates —SiO 2 on Si(001) oroctadecyltrichlorosilane (OTS) self-assembled monolayer terminated Si(001) surfaces— arediscussed. Thin films were deposited from a home-made Knudsen cell by using a hot-walldeposition technique. Films were analyzed by atomic force microscopy, X-ray diffraction, and X-rayreflectivity. Films exhibited a (001) orientation with a 1.63 nm d spacing, and a metastable thin filmphase was observed without any distinction of the nature of the substrate. However, differences werenoticed in the early stages of growth: PTCDI-5C/SiO 2 first monolayers presented a Stranski-Krastanov growth mode, whereas PTCDI-5C/OTS first monolayers showed a more complex mode with incomplete wetting of the substrate surface. Differences between the two morphologiessoftened as the film thickness increased

Surface Potential Visualization in Organic Antiambipolar Transistors Using Operando Kelvin Probe Force Microscopy for Understanding the Comprehensive Carrier Transport Mechanism

Abstract An antiambipolar transistor (AAT) exhibits a negative differential transconductance (NDT) due to a partially overlapped p–n junction formed in the transistor channel. However, the NDT origin remains unclear. In this study, the operando Kelvin probe force microscopy is employed to unveil this issue. When the AAT is turned on, steep potential drops induced by pinch‐off states are visible in the p‐ and n‐type channels. Due to the similarity to the surface potential profiles in the constituent transistors, it is revealed that the pinch‐off points are formed at both edges of the p–n‐stacked layers. This result indicates that the overlapped layers behave like a pseudo‐drain electrode for both transistor channels. Therefore, the AAT drain current can be explained as the overlapped currents in the saturation regions of the p‐ and n‐type transistors. Moreover, the drain current is suppressed when either the p‐ or n‐type channel is completely depleted. The depletion layer formation is responsible for the NDT property. This technique provides a comprehensive understanding of the carrier transport mechanism of AATs, leading to the further evolution of organic electronic circuits

Recent progress in photoactive organic field-effect transistors

Recent progress in photoactive organic field-effect transistors (OFETs) is reviewed. Photoactive OFETs are divided into light-emitting (LE) and light-receiving (LR) OFETs. In the first part, LE-OFETs are reviewed from the viewpoint of the evolution of device structures. Device performances have improved in the last decade with the evolution of device structures from single-layer unipolar to multi-layer ambipolar transistors. In the second part, various kinds of LR-OFETs are featured. These are categorized according to their functionalities: phototransistors, non-volatile optical memories, and photochromism-based transistors. For both, various device configurations are introduced: thin-film based transistors for practical applications, single-crystalline transistors to investigate fundamental physics, nanowires, multi-layers, and vertical transistors based on new concepts

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Interface Engineering for Controlling Device Properties of Organic Antiambipolar Transistors

The main purpose of this study is to establish a guideline for controlling the device properties of organic antiambipolar transistors. Our key strategy is to use interface engineering to promote carrier injection at channel/electrode interfaces and carrier accumulation at a channel/dielectric interface. The effective use of carrier injection interlayers and an insulator layer with a high dielectric constant (high-<i>k</i>) enabled the fine tuning of device parameters and, in particular, the onset (<i>V</i>_on) and offset (<i>V</i>_off) voltages. A well-matched combination of the interlayers and a high-<i>k</i> dielectric layer achieved a low peak voltage (0.25 V) and a narrow on-state bias range (2.2 V), indicating that organic antiambipolar transistors have high potential as negative differential resistance devices for multivalued logic circuits