Molecular-scale transistor

Thus, the ideas behind the bottom-up approach are as simple as powerful. The general aim lies in the design of novel materials employable for molecular-scale electronics, such as molecular transistors, molecular photovoltaic applications, molecular display technology, etc. Hereby, the functions are carefully adjusted by synthetic tools to build up a certain chemical structure. In this context, we need to address the key steps/challenges in such a work-flow. With this in hands the impetus of this thesis should be illustrated. 

A crossbar array based scheme is at the moment perceived as the most realistic strategy to combine nano-scale components with CMOS circuits [67], where a concept for neuromorphic networks based on molecular singleelectron transistors [68] has also been proposed. 

Khanna, V.K. (2004) Emerging Trends in Ultra-miniaturized CMOS (Complementary Metal-Oxide-Semiconductor) Transistors, Single-Electron and Molecular-Scale Devices ... 

A notable distinction needs to be made. Molecular materials for electronics deals with films or crystals that contain many trillions of molecules per functional unit, the properties of which are measured on the macroscopic scale, while molecular scale electronics deals with one to a few thousand molecules per device. For example, thin film transistors (TFTs) and polymer-based light emitting diodes (LEDs) utilize molecular materials for electronics. The grain size of many of these crystalline features in TFTs and LEDs is in the... 

Summarizing, we have tried to draw a consistent picture of P3HT at different length scales ranging from the molecular scale over the mesoscopic scale to the device level. The P3HT stmcture on the molecular and mesoscopic scale has been correlated with its optical, electrochemical, electronic, and opto-electronic properties, which provide the basis for its performance in transistor and solar cell devices. 

The gradual channel approximation (described above) may fail, as the channel length of the FET is shortened. The electrostatics of the FET limit L > 1.5 q in a molecular FET, where the dielectric constant of the gate dielectric layer and semiconductor channel may be similar [22, 23]. This is particularly important in monolayer transistors, as many monolayer FETs studied have been limited to tens of nanometers channel length by the tens of nanometers size of ordered domains, and therefore require thin gate dielectric layers. Only recently (described below) have routes been shown to form more extended ordered molecular monolayers, allowing micron-scale FET channel lengths to be explored. 

Thin polymer films have many possible technical applications. Transistors and light-emitting diodes are the obvious ones. In ultra-thin films, one may even approach an electronics of molecular dimension. Molecular electronics will be a future challenge for basic and applied science. Nature applies it on a large scale in the reaction centers of the photosynthetic process, where photoinduced mobile charges are separated in some analogy to the separation of the photo-(p-n)-pair in the junction zone of a semiconductor (see Section 13.3.1). 

One of the most promising bottom-up approaches in nanoelectronics is to assemble 7i-conjugated molecules to build nano-sized electronic and opto-electronic devices in the 5-100 nm length scale. This field of research, called supramolecular electronics, bridges the gap between molecular electronics and bulk plastic electronics. In this contest, the design and preparation of nanowires are of considerable interest for the development of nano-electronic devices such as nanosized transistors, sensors, logic gates, LEDs, and photovoltaic devices. 

---