SU1657954A1 - Method of determination of physico-mechanical characteristics of thin films - Google Patents

Abstract

The invention relates to a measuring technique and can be used in scientific research to determine the physicomechanical properties of thin films. The purpose of the invention is to increase the informative value of determining the informative value of determining the film thickness, speed and absorption of ultrasound in it. In a speaker system, standing waves are excited and the values of the first resonant frequencies fz and fi are measured with and without the film under study. Then, by changing the frequency of the RF filling of the ultrasonic pulses, the sample is transparent for the ultrasound and the frequency fa corresponding to this condition is measured, and the amplitudes AI and A2 of the output ultrasonic signals for the speaker with the test sample are measured at this frequency fa. and without it, respectively, the measured thickness d of the film, the propagation speed C of ultrasound and the absorption coefficient a in the film under study are determined using the following formulas f3 (f2-fi) / (f3 (f2-fi) / f2fi: 2f3 / C0- f2-fi / f2fiaf (f2- -fl) lnA2 / Ai. 1 ill. СЛ с

Description

The invention relates to a measuring technique and can be used in scientific research to determine the physicomechanical properties of thin films.

The aim of the invention is to increase the information content by determining the film thickness and the rate of absorption of ultrasound in it.

The drawing shows a diagram of a device that implements a method for determining the physicomechanical characteristics of thin films.

A device that implements the method contains an RF generator 1, a speaker system containing a radiating 2 and receiving 3 piezo transducers. immersion liquid 4 with known speeds of ultrasound Co and ultrasound absorption coefficient a (ultrasound), test sample 5, amplifier 6, oscilloscope 7, voltmeter 8, frequency meter 9 with two inputs a and b.

The method is carried out as follows.

An acoustic system consisting of two transducers installed so that their working surfaces are parallel to each other is placed in an immersion liquid 4 with known values soon

01

 u with -N

Since the propagation of ultrasound and the absorption coefficient of ultrasound in it, is sounded by continuous ultrasonic vibrations.

By varying the oscillation frequency of the ultrasound with the aid of the generator 1 and controlling the amplitude of the ultrasonic signal with the aid of a voltmeter 8 and an oscilloscope 7, one obtains a resonance condition at which standing waves occur in the acoustic system. Frequency meter 9 on input b measures the first resonant frequency fi, for which it follows from the resonance condition

liquid 4 and, maintaining the ultrasonic signal at the same frequency fa, measure the amplitude A2 of the ultrasonic signal received at this frequency at the output of the speaker system.

The ultrasonic absorption coefficients a and a0 in a speaker system with and without a sample, respectively, satisfy the following relations:

exp ct0 (L-d) + ad;

exp a0L,

(4) (5)

-Ј

where L is the distance between piezo transducers 2 and 3.

Next, an acoustic system with an immersion liquid with a known ultrasonic propagation speed Co and ultrasonic absorption coefficient a put test sample 5 between two ultrasonic transducers 2 and 3 so that the working surfaces of transducers 2 and 3 and sample 5 are parallel to each other.

By varying the oscillation frequency of the ultrasound with the help of generator 1, a resonance condition is reached, at which a standing wave occurs in a given speaker system with the sample, and a frequency meter. 9, at input b, the first resonant frequency f2 is measured, for which it follows from the resonance condition

f2

With

2 (Ld-l-Co / c-d)

(2)

Then, pulses of ultrasonic vibrations are excited in the acoustic system and, by changing the frequency of the high-frequency filling of the ultrasonic pulses, the condition of transparency of the sample 5 is achieved and the frequency fa corresponding to this condition is measured with frequency meter 9. Since, under the condition of transparency of the sample, half the wavelength is laid over the sample thickness, i.e. I 2d, it follows from the transparency condition that

d

From 2f3

where C is the velocity of the ultrasonic wave in the sample.

At the same time, a voltmeter 8 measures at the output of the speaker system the amplitude AI received at the frequency b of the ultrasonic pulse signal.

Then, test sample 5 is removed from the speaker system from the immersion

15

20

25

where AO is the amplitude of the ultrasonic wave at the input of the speaker system;

AI and A2 - the amplitude of the ultrasonic wave at the output of the speaker system with and without a sample, respectively;

L is the distance between piezo transducers 2 and 3.

Measure fi, f2. fa, AI, A2, and solving the system of equations (1) - (5) with respect to d, c, and a, determine them using the following derived formulas:

0

d

With

2f3

1 + Mf2Z ± b

f2 - f i J

With With

 -f

(6) (7)

a - “o +

2f3

f2-fl

A2 Co f2fl + f3 (f2 - fi) | P AT (8)

40

45

50

55

The method for determining the thickness of thin films, the absorption coefficient and the speed of ultrasound propagation over their thickness allows, firstly, to obtain a definite quantity with a given accuracy with a smaller number of measurements, and second, to investigate the physical processes that result in end changes (for example, , with changes in temperature regimes of the studied samples or with changes in mechanical loads along these samples).

In addition, the method allows determining the values of the three parameters c, and, required for characterizing the physicomechanical properties of film materials, and eliminates the need to use additional devices (optical, mechanical, etc.) for independent purposes. determining, which significantly reduces the material costs of their equipment, installation, maintenance, and also eliminates the need to take into account additional errors associated with the various effects of external factors actors on various conditions of independent experiments.

Claims (1)

The invention of the method for determining the physicomechanical characteristics of thin films, namely, that in the acoustic system containing the radiating and receiving ultrasonic transducers placed in the immersion liquid, the test film sample is placed in such a way that the working surfaces of the transducers and the film sample under study are parallel - between themselves, excite ultrasonic vibrations, measure the amplitude characteristics of the signals from the output system of the acoustic system with a sample of the film and without it. Physicomechanical characteristics of a sample of a film are determined by measured oscillations according to measured values, characterized in that, in order to increase the informativity, by determining the film thickness and the ultrasound absorption rate in it, standing waves are measured and the values of the first resonant frequencies fi and f2, respectively, with and without a film, then excite ultrasonic oscillations in a speaker system with a sample of a film, change their frequency to obtain a frequency fa at which the amplitude AI is maximum, then measure the amplitude A2 of the output at the same frequency fa pulsed ultrasonic vibrations for a speaker system without a film sample and from measured values determine the thickness d of the film, the speed C of ultrasound propagation and the absorption coefficient in the sample of the film under study Ulam: where is co. "O - respectively, the speed and absorption coefficient of ultrasound in an immersion liquid.