D. A. Nasimov

SOI nanowires as sensors for charge detection

The properties of silicon-on-insulator nanowires (SOI NWs) fabricated by means of electron lithography and gas etching of SOI in XeF2 or SF6:CFCl3 have been investigated. The method used to fabricate the nanowires was found to require no additional anneal to be given to the final structure for defect removal after nanostructuring. The sensitivity of SOI NWs to negative protein BSA molecules in the pH 7.4 buffer solution was shown to be as high as 1 femtomoles. The gate characteristics of SOI NWs were used to determine the charge density of particles adsorbed on the NW surface. A charge density of 4.6 × 1011 cm−2 was estimated for a 1 femtomole protein concentration. The combined use of open-channel structures with top gates was employed for determining the charge state of structure surfaces after different chemical treatments. Chemical treatments giving rise to a density of the negative charges on the surface of NWs ranging in the interval (7–23) × 1011 cm−2 were examined. Treatments in methanol (after removal of the native oxide) were found to provide stabilization of the SOI surface over a 3-h interval after the treatments.

Silicon nanowire transistors for electron biosensors

A method of nanostructuring of silicon-on-insulator (SOI) layers on the basis of gas etching in XeF2 or SF6:CFCl3 is developed for the purpose of obtaining SOI nanowire structures. SOI nanowire transistors (SOI NWTs) with free channels, used as sensors in electron detectors, are fabricated and tested. The results of experiments show that the method used to fabricate nanowires requires no high-temperature operations for elimination of defects after nanostructuring of SOI layers. The sensitivity of SOI NWTs to test molecules of bovine serum albumin is 10−15 mole/liter, which is one of the best results for nanowire biosensors.

SOI-nanowire biosensor for detection of D-NFATc1 protein

The nanowire (NW) detection is one of the fast-acting and high-sensitive methods, which can recognize potentially relevant protein molecules. A NW-biosensor based on the silicon-on-insulator (SOI)-structures has been used for biospecific label-free real time detection of the NFATc1 (D-NFATc1) oncomarker. For this purpose, SOI-nanowires (NWs) were modified with aptamers against NFATc1 used as molecular probes. It was shown that using this biosensor it is possible to reach sensitivity of 10−15 M. This sensitivity was comparable to that of the NW-biosensor with immobilized antibodies used as macromolecular probes. The results demonstrate that approaches used in this study are promising for development of sensor elements for high-sensitive diagnostics of diseases.

SOI nanowire transistor for detection of D-NFATc1 molecules

Nanowire (NW) detection is one of the fast and highly sensitive methods. An NW biosensor based on silicon-on-insulator (SOI) structures are used in the reported study for real-time label-free biospecific detection of the NFATc1 (D-NFATc1) cancer marker. For this purpose, the SOI NWs are functionalized with NFATc1 aptamers used as macromolecular probes. It is demonstrated that such a biosensor can ensure a detection limits up to 10−15 M, which is comparable with the sensitivity ensured by an NW biosensor with immobilized antibodies used as macromolecular probes. The results of this study demonstrate that such approaches to the development of sensor elements for highly sensitive diagnostics of diseases are really promising.

Ultra-thin SOI Layer Nanostructuring and Nanowire Transistor Formation for FemtoMole Electronic Biosensors

In this work nanostructuring of SOI layers with tenth nanometer thickness was made at last stage of electronic biochip producing using fluorine gas-plasma content etching. Electrical characterization verities that used fabrication approach produces high-quality devices operating up to temperatures close to liquid helium. The sensitivity of SOI NWs to negative ions Cl- in aqua solution (pH 6) was shown to be as high as 10 femtoMoles. The sensitivity of SOI NWs to negative protein BSA molecules in pH 7.4 buffer solution was shown to be as high as 1 femtoMoles.

Two-dimensional photonic crystals fabrication and close-packing by electron-beam lithography

It is brought an approach of creation and close-packing two-dimensional photonic crystals with given sizes of elements by the EBL. The main problems of formation these structures were considered.

Atomic Steps on a Single-Crystal Surface Studied With in Situ Uhv Reflection-Electron Microscopy

Ultra-high vacuum reflection electron microscopy and atomic force microscopy were used to study atomic steps on the Si(111) surface, with the focus on the structural and morphological transitions during gold adsorption and oxygen treatments. Subsequent stages of gold three-dimensional island nucleation with different morphologies in a wide temperature range of the substrate were imaged. The influence of the monatomic step density on the redistribution of the three-dimensional islands was revealed during thermal annealing of the substrate. Investigations of the structural transformations of the silicon surface during oxygen treatments were performed in the temperature range 500-900°C Monatomic step movements in the step-up direction and negative island formation due to vacancy nucleation were imaged. The dependence of the step velocity on the width of neighbouring terraces was measured. The intensity oscillations of the high-energy electron beam reflected from the silicon surface was found to be caused by a periodic change of the surface morphology due to formation of two-dimensional negative islands.

[SOI-nanowire biosensor for the detection of D-NFAT 1 protein].

The nanowire (NW) detection is one of fast-acting and high-sensitive methods allowing to reveal potentially relevant protein molecules. A NW biosensor based on the silicon-on-insulator (SOI)-structures was used for biospecific label-free detection of NFAT 1 (D-NFAT 1) oncomarker in real time. For this purpose, SOI-nanowires (NWs) were modified with aptamers against NFAT 1 used as molecular probes. It was shown that using this biosensor it is possible to reach the sensitivity of ~10(-15) M. This sensitivity was comparable with that of the NW biosensor with immobilized antibodies used as macromolecular probes. The results demonstrate promising approaches used to form the sensor elements for high-sensitive disease diagnostics.

Formation of two-dimensional photonic crystals by electron-beam lithography

The approach to formation of two-dimensional photonic crystals with preset sizes of elements by the electron-beam lithography (EBL) is presented. The main problems appearing during formation of these structures are considered.