Exercise 7. Translate the text in written form.

Combining nanoscale manipulation with macroscale relocation of single quantum dots

Techniques such as scanning probe microscopy and transmission electron microscopy have been used extensively to provide crucial high-resolution structural and morphological information on nanoscale systems. Measurement of the optical properties of a nanostructured material or nanoscale device with a resolution comparable to the length scale of the system of interest, however, continues to present a challenge. A number of techniques have been developed to push the resolution of optical microscopy and spectroscopy to the single-molecule/particle limit. These include scanning near-field optical microscopy (SNOM) and techniques based on adaptations of single-molecule spectroscopy, such as fluorescence imaging with one-nanometer accuracy (FIONA), stochastic optical reconstruction microscopy (STORM). These techniques require the fluorophore under observation to be isolated by distances larger than the diffraction limit of the microscope. The study of single fluorophores separated by distances larger than the diffraction limit has proven to be a valuable tool in understanding the optical properties of a broad range of nanostructured systems, including conjugated polymers, biomolecules , and quantum dots . Nonetheless, these techniques fundamentally rely on a statistical distribution of molecules and are therefore not optimal for the study of specific isolated nanostructures at well-defined locations on a surface. Recent attempts at the positioning of quantum dots (QDs) based on electro-osmotic flow control (EOFC) have resulted in a positioning precision of 130 nm when particle diffusion is suppressed. In a challenging recent experiment, atomic force microscopy (AFM) was used to manipulate a single gold nanoparticle (≈35 nm) to approach a single quantum dot. The gold nanoparticle was shown to dramatically quench the optical lifetime of the QD and to completely suppress its blinking.

UNIT 3

Read and translate the text and learn terms from Essential Vocabulary:

SINGLE ELECTRON TRANSISTOR

Just like metal-oxide semiconductor field-effect transistors (MOSFETs) and MOS capacitors, to understand the fundamental principles of SETs, we need to start with a single-electron capacitor (SEC), which is the simplest known single-electron device. Also called a single-electron box, the capacitor usually consists of a quantum dot that is asymmetrically located between two electrodes. The capacitance between the quantum dot and the closer source electrode is the tunnel junction, and the other electrode is called the control gate capacitor. Once we apply voltage across two electrodes, electrons will be injected into quantum dots or, vice versa, ejected from quantum dots through the tunneling junction depending on the signs of the voltages. This is the same for any charge storage media between two electrodes. The difference in the case of the single-electron box is that because of the size of quantum dots, every time we try to inject an additional electron into quantum dots, excessive energy is needed due to Coulomb blockade effect. This unique property enables us to control the motion of a single electron through tunnel junctions. The Coulomb blockade is caused by an increase in the excessive charging energy due to the smaller size of quantum dots. Strictly speaking, it is not a quantum effect but rather a classic phenomenon under the effect of nanometer size.

The discovery of the transistor has clearly had enormous impact, both intellectually and commercially, upon our lives and work. It also led to the microminiaturization of electronics, which has permitted human to have powerful computers that communicate easily with each other via the Internet. Over the past 30 years, silicon technology has been dominated by Moore’s law: the density of transistors on a silicon integrated circuit doubles about every 18 months. To continue the increasing levels of integration new approaches and architectures are required. In today’s digital integrated circuit architectures, transistors serve as circuit switches to charge and discharge capacitors to the required logic voltage levels. Artificially structured single electron transistors studied to date operate only at low temperature, but molecular or atomic sized single electron transistors could function at room temperature.

The effects of charge quantization were first observed in tunnel junctions containing metal particles as early as 1968. Then the idea that the Coulomb blockade can be overcome with a gate electrode was proposed by a number of

researchers, and Kulik and Shekhter developed the theory of Coulomb-blockade oscillations, the periodic variation of conductance as a function of gate voltage. Their theory was classical, including charge quantization but not energy quantization. However, it was not until 1987 that Fulton and Dolan made the first SET, entirely out of metals, and observed the predicted oscillations. They made a metal particle connected to two metal leads by tunnel junctions, all on top of an