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computer modelling of process of interaction of a sonde of a power tunnel microscope with the sample on an example of system copper (sonde) - gold (sample)

C help CTM probably to carry out examinations of local electronic structure of spending surfaces with nuclear the resolution. The knowledge of structure of sonde CTM is important for qualitative interpretation of data CTM with the nuclear resolution, improvements of parametres of the spatial resolution as the electronic structure of an edge of a sonde influences requirements of tunneling of electrons in different sites of the sample.

It is known, that the essential part of errors of measurings nanorelefa surfaces a tunnel microscope can be caused features of traffic control of a sonde [161,162,163]. Thus, on the one hand the account of geometry of an edge of a needle at interpretation of measurings allows to reduce essentially the contribution of the specified errors, the patented methods of processing of the images, conformity of a relief of a surface raising level to physical requirements of scanning [164] on the other hand are already developed.

In connection with the above-stated, mathematical modelling of change of the shape and the sizes of an edge in the course of scanning is actual and there is a possibility, using available observed datas nanorelefa to spot them from mathematical model of process of scanning. Influence on gained effects of scanning can render oscillations of the warrant of a tunnel microscope, and and oscillations podvesa a sonde [165]. However use tenzoplatform and laboratory tables with an antivibrating coat by present time allows to lower essentially a degree influence of the above-named factors.

One of appendices CTM and spectroscopies is examination of heterogeneity of electrical properties of samples of the difficult composition. In this case the joint analysis of morphology of a surface and Vakh, removed in various points of a surface, allows to judge allocation of various phases to surfaces

Composit structures to explore correlations between technological parametres of their reception and electronic properties. We [166] had been studied earlier influences of parametres of tunnel system by sight BAX on an example of modelling system an edge (tungsten) - the sample (gold). After a series of measurings Vakh made without replacement of an edge, it is erected, that corresponding to one of the first skanov the curve is unsymmetrical concerning a voltage sign that testifies to influence of electronic structure of an edge. At carrying out of nonsingle measurings with the same edge dependence becomes symmetrical concerning a voltage sign. From this it is possible to draw a deduction, that the electronic structure of an edge has changed, that can be explained massoperenosom from the sample on an edge. It is necessary to score, that in most general case the shape of a tunnel barrier depends on work functions from materials of the sample and an edge, the enclosed voltage, distance between electrodes. Besides, it is necessary to consider potential of forces of the mirror image. Calculations BAX carried out earlier show, that the account of potential of forces of the mirror image leads to distinctions not only in values of a tunnel current, but also in the form of curves [167]. We will score, that at voltage change between an edge and the sample there can be also the thermal warming up of an edge caused by energy, oozed in pripoverhnostnoj fields of an edge in the course of tunneling of electrons (the thermal expansion of an edge related to an energy liberation of Joule - the Disposition to laziness, and the thermal expansion of an edge related to energy liberation Nottingama) [168].

This effect influences on BAX a tunnel barrier since the backlash breadth depends on the enclosed voltage. Besides, calculations [168] have confirmed possibility of avalanche magnification of the current leading to formation of an electrical link between an edge of a sonde and a surface of the sample. Prominent feature of this process is the abrupt slope of resistance of a tunnel gap at the appendix of a modifying impulse of a voltage. Thus change of temperature of vertex of an edge can be not so great (the order 150 Λ "). It is necessary to score, that, for example, for

Measurings BAX presence of mechanical contact between a fashion and an edge or even partial transport of substance of an edge on the sample is unacceptable, however the given technology can be used at embodying of the superficial updating in nanometrovoj fields of the sample with use CTM [169-172]. By present time there is an expedient of reception of sondes with the given electronic structure at use of the oriented monocrystal needles with in advance known crystallographic structure [173], an actual problem is modelling of the processes occurring at technological use of a sonde.

As it was already scored in point 4.2, modelling of interaction of an edge of a sonde (copper) with a surface the sample (gold) in the course of sonde heating at passage of a tunnel current for various configurations of an edge has been yielded by a Monte-Carlo method (the Metropolis plan [156]).

For the interaction description multipartial potential Gupta, (as well as other metal potentials, it is multipartial and depends on local density) which has well proved for the description of metal systems [151,152] was used. Potential Gupta is in detail featured by us in point 4.1. In table 1 parametres for system copper - gold [151,152] are presented.

Table 1. Parametres of potential Gupta for system copper - gold.

Parametres Au-Au Si — Au Cu-Cu
ζ 1.7900 1.5605 1.2240
rO 2.8840 2.5560 2.5560
P 10.229 11.050 10.960
q 4.0360 3.0475 2.2780
AND 0.2061 0.1539 0.0855

Copper is chosen as metal, of which the sonde, as parametres of potential Gupta for system tungsten - gold is made (tungsten
The wire is traditionally used for manufacturing of sondes in CTM [173]) in the literature do not meet, that, our way to opinion, will not change qualitatively effects of modelling.

On fig. 30-33 evolution of system an edge - the sample before carrying out of process of modelling for various configurations of an edge is shown: a core and a cone, and also for various distances between the sample and a sonde edge in an initial configuration. It is obvious, that the thermal protraction of an edge of a sonde can give as mechanical contact between the sample and an edge (fig. 30-32 see), and in partial transport of substance of a sonde on the sample (the case is figured on fig. 33). The initial configuration corresponds to a room temperature 293К. In cases modelled by us for a configuration the cone makes change of temperature 150JT, and for a core case - 177 To, that is in the good consent with effects of operation [168].

Let's score, that at examination of performances of tunnel contact metal - metal (in particular, receptions Vakh) is necessary the careful account of the parametres influencing a tunnel current, for extraction of the information on electronic structure of the sample. The shape and breadth of a tunnel barrier and their change from the enclosed voltage make essential impact on obtained data. The detailed account of a transparency of a tunnel barrier is necessary for the analysis of experimental data. And the effect of thermal expansion of an edge makes essential impact on the shape of volt-ampere characteristics of system even at small in comparison with a work function bias voltages. In this case change of length of an edge occurs in the core at the expense of thermal expansion. It has been thus observationally erected [168], that the contribution of energy of Joule - the Disposition to laziness prenebrezhimo is small in comparison with the contribution of energy Nottingama. Thus the edge thermal dilatation can reach quantities, comparable with breadth of a tunnel gap, and occurrence of avalanche process of a thermal dilatation of the edge leading to occurrence of contact between an edge of a sonde and a surface of the sample is possible.

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Fig. ZO. System an edge - the sample to (the upper drawing) and after carrying out (the inferior drawing) modelling process. A sonde configuration - a cone. The distance between the sample and an edge in an initial configuration makes 0,1 nanometers.

Fig. 31. System an edge - the sample to (the upper drawing) and after carrying out (the inferior drawing) modelling process. A sonde configuration - a cone. The distance between the sample and an edge in an initial configuration makes 0,15 nanometers.

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Fig. 32. System an edge - the sample to (the upper drawing) and after carrying out (the inferior drawing) modelling process. A sonde configuration - a core. The distance between the sample and an edge in an initial configuration makes 0,1 nanometers.

Fig. 33. System an edge - the sample to (the upper drawing) and after carrying out (the inferior drawing) modelling process. A sonde configuration - a core. The distance between the sample and an edge in an initial configuration makes 0,15 nanometers.

As the proof of it the modelling of interaction of an edge of a sonde spent by us with a surface of the sample in the course of sonde heating serves at passage of a tunnel current. Quantity of a thermal protraction of an edge and its strain at a heating of a needle a current proceeding in system an edge - the sample, is spotted by a material of which it is made. Despite that fact, that formation process nanostruktur on a surface of the sample has likelihood character and depends on amplitude of an impulse of a voltage (and accordingly quantities of thermal expansion of a sonde), the given technology can be used in nanolitografii [174]. It is necessary to score, that presence of mechanical contact is unacceptable for measuring BAX between a fashion and an edge or even partial transport of substance of an edge (see the inferior picture on fig. 33 after carrying out of process of modelling) on the sample, however the given technology can be used at embodying of the superficial updating in nanometrovoj fields of the sample with use CTM [169].

Let's note, as for use ACM also an actual problem is the account of influence on an interaction pattern as possible contact interaction of sonde ACM and the sample, and the dimensional superficial effects related to its shape. So, in operation [175] computer modelling of contact interaction of sonde ACM with a surface of an is non-linear-elastic polymeric material has been spent. It is shown, that the sonde geometry, and also distance between its vertex and a surface of the sample are the key factor spotting intermolecular and superficial forces of interaction.

2.4.4.

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A source: Antonov Alexander Sergeevich. MORPHOLOGICAL PERFORMANCES And FRAKTALNYJ the ANALYSIS of METAL FILMS ON the DIELECTRIC SURFACES. The DISSERTATION on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2017. 2017

More on topic computer modelling of process of interaction of a sonde of a power tunnel microscope with the sample on an example of system copper (sonde) - gold (sample):

  1. about carrying out of computer experiment on modelling of interaction of a sonde of a scanning microscope with the sample and an estimate of the dimensional and temperature gamut for regular functioning
  2. about a procedure of preparation of samples for studying fraktalnoj dimensionality and electrical properties of contact a sonde-sample by means of a scanning tunnel microscope
  3. about modelling of the shape of a sonde and the mechanism of its interaction with the sample
  4. examination of electrical performances of tunnel contact a sonde-sample
  5. Chapter 3. Examination of morphology of a relief, fraktalnyh properties of a surface and electrical performances of contact a sonde-sample for nanorazmernyh metal films on the dielectric substrates a method of scanning tunnel microscopy
  6. Chapter 1. The up-to-date state of examinations in the field of studying of morphological performances nanochastits and electrical performances of tunnel contact a sonde-sample methods nuclear, zondovoj and tunnel microscopy
  7. about application of potential Gupta for the intermolecular interaction description between a sonde and the sample
  8. 3.1. Examination of morphology of a relief and fraktalnyh properties of the sample «gold on mica»
  9. 3.3 Comparison of effects on examination fraktalnyh properties nanorazmernyh films of gold, argentum: atomno-power and tunnel microscopy
  10. 8.1. A statistical sample piece of process
  11. 8.2. The dynamic mathematical sample piece of process
  12. 8.2.8. Imitating modelling of a master schedule and an estimation of adequacy of a sample piece according to pilot plant work.
  13. Korostelev,. a sample piece of stationary physical fields and criterion of MGD-STABILITY In algorithms of a dynamic sample piece of an aluminium electrolytic furnace / the Dissertation / Moscow, 2005
  14. sonde manufacturing
  15. measuring of volt-ampere characteristics of tunnel contact tungsten - gold
  16. 1.5 About processing of the images gained by the scanning tunnel microscope «UMKA - 02G»
  17. an estimate of the dimensional and temperature interval of regular functioning of a scanning tunnel microscope for studying of separate sites of a surface
  18. 2.2.4.1 Sample SAM
  19. § 3. The Legal regime of the industrial sample
  20. Measuring of a roughness of a surface of the explored sample