SU1520609A1 - Tunnel microscope - Google Patents

Abstract

The invention relates to electronic engineering, in particular, to microprobe instruments, in which a tunneling current is used for surface investigation. The purpose of the invention is to reduce the size and simplify the design of a tunneling microscope - achieved by combining the functions of scanning the tip and positioning it relative to the object holder in one structural unit. The microscope contains a base and a temperature compensated scanning unit of two tubular coaxial piezoelectric elements. The mutual positioning unit is formed by fixing the scanning unit in a case movable relative to the base along the free end of the external piezoelectric element. The body is fixed relative to the base by the friction force, which is greater than the forces arising from scanning the tips, and less than the forces developed by the external piezoelement if a saw-tooth voltage is applied to its electrodes and asymmetrical pulse fronts. 2 Il.

Description

The invention relates to electronic engineering, in particular, to microprobe devices, in which a tunneling current is used for surface investigation.

The purpose of the invention is to reduce the size and simplify the design of the tunneling microscope by combining the functions of scanning the tip and its mutual positioning relative to the object holder in one structural unit.

Figures 1 and 2 show a tunnel cell with a vertical and horizontal axis of the tip, embodiments of which are shown.

The tunneling microscope contains a thermocompensated scanning unit consisting of two coaxially arranged and fastened together adjacent ends of tubular piezoelectric elements 1 and 2. A pin 3 is fixed on the free end of the internal piezoelectric element 1. The external piezoelement 2 is fixed by the second end of the body 5 relative to the base 4 The body is fixed relative to the base by the force of friction in a direction parallel to the axis of the piezo element. The value of the force of friction Q must be within

f X, M, kQ fl. + M,),

where f, f is the maximum frequency

changes in the length and resonance frequency of the internal and external piezoelements, respectively, s;

x, Xg g maximum changes in the lengths of piezoelements during the application of stresses to them, m; M ,, Mj - masses of piezoelectric elements,

kg;

k is the coefficient of friction nor to between the body and the base; Q is the clamping force of the case and

base kg

In the vertical position of the tip 3 (Fig. 1), the clamping is carried out, for example, by elastic elements 6, and in the horizontal position (Fig. 2), the clamping is provided by the weight of the assembly, t, in this case

Q (M, + M. + M) g,

where M is the body weight, kg;

g - free fall acceleration, m / s o

The internal piezoelectric element 1 has a split electrode for controlling the scanning of the tips in three coordinates, and the output electrodes of the external piezoelectric element 2 are connected to the output of the sawtooth voltage source 7 with asymmetric pulse fronts

The microscope works as follows.

When applying a sawtooth voltage from source 7 to the electrodes of external piezoelectric element 2, it changes its length slowly with a gentle front of the pulse and quickly with a steep front of the pulse. When slowly changing the length of the body 5 does not move relative to. on the base 4 "With a sharp change in length, the inertia force exceeds the friction force, the body 5 slips against the base" After the tip 3, fixed on the scanning unit 1, approaches

to object holder 8, transition to scanning mode in which external piezoelectric element 2 does not participate due to the fact that the mass of the internal piezoelectric element 1 is much less than the mass

the external inertial forces arising during scanning are substantially less than the frictional force between the movable body 5 and the base 4, therefore the body does not move during the scanning,

Example. Parameters internally. go of the piezoelectric element - length 20 MMJ wall thickness 0.5 mm; outer diameter 10 mm; operating frequency Hz; maximum displacement x 10 m; weight (with point) M 6-10 kg „

The parameters of the external piezoelectric element - length 27 mm; wall thickness 1 mm; outer diameter 18 mm; working frequency fo 2-10 Hz; maximum

X 10 m; weight N 14-10 kg.

The friction coefficient is adopted, 3, which is true for a wide class of materials. The mass of the housing 5 is 20 g, the clamping force must be greater than 130 g. Therefore, in the embodiment

(FIG. 1) the pressing force can be selected within

130; Q; 268.

Similar calculations are made for other options.

Claims (1)

Invention Formula A tunneling microscope containing a base, a temperature-compensated scanning unit, made of two coaxially arranged and fastened between each other by the end ends of tubular piezoelements, on the inner side of which a point is installed on the free end, the node of the mutual positioning of the tip and the object handler are inclinable relative to the base housing and the power supply system of the piezoelectric elements, characterized in that, in order to reduce the size and simplify the structures, the power supply system is equipped with A sawtooth voltage with asymmetrical pulse fronts, the output of which is connected to an external piezoelectric element, and the mutual positioning unit is formed by .1 Editor A „Motyl "Y. 2 Compiled by Vogavrushin Tehred L. Serdyukova Proofreader T. Malets Order 6765/54 Circulation 696 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Subscription