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3.3 Teplovizionnyj the control of monocrystals of germanium.

For an estimate of homogeneity of the transparent optical materials besides direct optical methods probably use teplovizionnyh the measurings related to recording of allocation or oscillations of temperatures on a surface of explored samples [122-125].

Teplovizionnym a method probably researcher as existing flaws by realisation of an exterior (active) heating and to reveal the induced inhomogeneities arising while in service optichesih of devices on the basis of crystals and glasses (the passive control). Such inhomogeneities arise, in particular, as at the expense of uptake
Radiations, and at the expense of a heating of electronic devices of devices, that, in turn, leads to a non-uniform heating of optical devices.

One of the minor problems teplovizionnogo the control are superimposition on a pattern of an explored temperature field of object of stray electromagnetic radiation IK of a gamut (thermal radiation) both from an exterior environment, and from most teplovizionnoj cabinets. And if shielding allows to get rid of exterior noise effect of a multiple reflexion echo in system a monocrystal device - optical system teplovizora, well observed in the absence of a heating (fig. 3.17) to cut it is impossible, and the unique solution of the given problem is bias of the sample concerning an optical axis teplovizora in a band of lack of reflexion (the plan is presented on fig. 3.18).

Fig. 3.17. Reflexion teplovizionnoj cabinets from the sample of germanium,

Leading to contortion of data about temperature

Fig. 3.18. The plan of examination of monocrystal samples with the help

teplovizora at the active thermal control

In the present operation for experimental researches MACH was used teplovizor firms FLIR, model Т250, imported to the state register of SI of the Russian federation under the number 41736-09, together with specialised software FLIR ResearchIR.

Table 3.1 the basic technical characteristics teplovizora «FLIR Т250»

Parametre Value
Temperature sensitivity (NETD) 80 mk at 30oC
The ik-resolution 240? 180 pixels
Gamut of measurings of temperatures of a subject От-20 oC to +350 oC
Review field / the minimum focal

Distance

25o? 19 °/0.4 m
Spectroscopic gamut 7 microns
Frequency of updating of the image 9 Hz
Accuracy ±2oC Or 2 % from the indication
The allowance on radiation coefficient Varies from 0.01 to 1.0 or gets out of the list of materials

At measuring of temperature with the help teplovizionnyh devices such parametres as humidity, air temperature, distance to object and radiation coefficient (a blackness degree are considered

Surfaces - ε).

And if accuracy of definition of atmospheric performances incidentally influences accuracy of definition of temperature incorrectly certain coefficient of radiation depending on a material and a relief of a surface, imports notable contortions.

For an estimate of influence of the given parametre experiments on the polished sample of a monocrystal of germanium in which course the sample was exposed to a prompt heating have been made. The analysis was spent by means of the temperature lateral views which are one of tools ON. Three lateral views were imposed on one straight line, and values of coefficient of radiation - 0,4, 0,6 and 0,8 were set. (Fig. 3.19). C by the help of the software for everyone temperature a lateral view it has been found the peak and underload temperatures, and also the difference between these values (Dt) is calculated. According to the gained effects, the error in definition of value of coefficient of radiation in limits ±0.02 gives contortions within a device error. Also that fact is scored, that at the given coefficient of radiation it is essential below actual, the magnification of sensitivity of the device to temperature lapse rates and, as consequence, to definition of structural heterogeneity of the sample though the temperature spotted thus strongly differs from the real is observed.

Fig. 3.19. Temperature a lateral view of a crystal of germanium at various coefficients of radiation (Lil - ε =0,4; Li2 - ε =0,6; Li3 - ε =0,8)

Following step was measuring of the true values of coefficient of radiation for monocrystals of germanium with various parametres of a roughness of a surface. Samples of monocrystals of the germanium, grown up by an expedient Chohralsky in a direction (111), alloyed by antimony (concentration of an impurity 1,4 have been for this purpose prepared? 1014

About

cm ^, conductivity/7-type).

Fig. 3.20. Samples of germanium with various processing of a surface: and - an abrasion powder М28, - an abrasion powder М10, in - the polished sample, g - the raw sample

Surfaces of samples were exposed to processing by grinding powders different dimensionalities (abrasion) and diamond pastes (polish). The abrasion was spent by water suspension of a powder

Electrocorundum: powder М40 on a glass substrate, М28 (fig. 3.20а the intermediate abrasion) on a glass substrate, powder MlO fig. 3.206 (a thin abrasion). A polish of samples spent to 4 stages: processing by diamond pastes 5/3, 3/2, 2/1 and 1/0 on cloth rice 3.20в.

Also the sample which surface was generated in process raspila a crystal fig. 3.20т, to any additional processing it has been prepared was not exposed.

The estimate of parametres of the gained surfaces was spent on optical profilometre NanoMap 1000WLI fig. 3.

Fig. 3.21. Three-dimensional a lateral view of the surface gained after an abrasion by powder MlO

Fig. 3.22. A surface site, shlifovannoj powder М28, presented in the form of a card of heights

Fig. 3.23. Three-dimensional a lateral view of the surface gained for the polished

Surfaces

Processing of the gained data was spent by means of program SPIP (The Scanning Probe Image Processor). Parametres of unevennesses of a surface are presented in table 3.2 according to ISO 25178.

Table 3.2. Parametres of unevennesses of surfaces of germanium

Ra. Nanometer

(A medial arithmetic diversion of unevennesses of a lateral view)

Rz, nanometer

(Height of unevennesses of a lateral view on ten points)

Rmax, nanometer (the greatest height of a lateral view)
Abrasion M 28 410 1340 1496
To abrasions 10 206 850 960
Polish 3 (2,70) 16 (15,90) 18 (17,70)

Measuring of coefficient of radiation was yielded as follows. To nagretomu to the sample the thermoelectric couple connected to a measuring instrument of temperature CENTER 304 fastened, and temperature comparison on exponents from a measuring instrument of temperature and with teplovizora was yielded at various values of coefficient of radiation (fig. 3.24).

Fig. 3.24. A heat pattern showing arrangements of the thermoelectric couple and a point

Examinations teplovizorom

Effects of examination are presented in the form of diagrammes in a following view: on an abscissa axis values on the thermoelectric couple, on an axis of ordinates - an odds between temperatures on the thermoelectric couple and on teplovizore (fig. 3) are specified.

Fig. 3.25. Values of temperature on the thermoelectric couple and an odds of temperatures on

To the thermoelectric couple and teplovizore for the polished surface

In drawing 3.25 the difference of temperatures of a surface of the polished sample of a monocrystal of the germanium, measured by the thermoelectric couple and teplovizorom is presented, at the exposed value of coefficient of radiation 0,75 and 0,77. From the given dependence it is possible to observe, that at temperature from 40oC to 60oC with the exposed coefficient of radiation of 0,77 indications of temperature on teplovizore and the thermoelectric couple practically coincide, the odds between values of temperature on the thermoelectric couple and teplovizore is underload. At the exposed coefficient of radiation in 0,75 underload discrepancies of temperature on the thermoelectric couple and teplovizore observed at temperature more low 40oC.

In drawing 3.26 the similar pattern only for the sample which surface is handled by powder М10 is observed. Exhibiting of coefficients of radiation on teplovizore was yielded in the range of values from 0,76 to 0,79. At temperature to 450C the least discrepancy of exponents of temperature on the thermoelectric couple and teplovizore at coefficient of radiation 0,79, with 450C to 60oC at 0,78, with 60oC to 70oC at 0,76, with 70oC to 80oC at 0,77.

Fig. 3.26. Values of temperature on the thermoelectric couple and an odds of temperatures on the thermoelectric couple and teplovizore for a surface handled by powder MlO

Fig. 3.27. Values of temperature on the thermoelectric couple and an odds of temperatures on the thermoelectric couple and teplovizore for a surface handled by powder М2 8

In drawing 3.27 dependence of temperatures of a surface of the sample handled by powder М28 is presented, at the coefficients of radiation exposed in the range from 0,79 to 0,81. On a drawing it is visible, that at the exposed value of coefficient of radiation on teplovizore 0,81 underload discrepancy of temperatures to 40C, from 40oC to 50oC corresponds

To value of coefficient of radiation 0,8; from 50oC to 60oC - 0,79, and after 60oC the least discrepancy of temperature registered on teplovizore and the thermoelectric couple, is observed at coefficient of radiation 0,79.

Fig. 3.28. Values of temperature on the thermoelectric couple and an odds of temperatures on the thermoelectric couple and teplovizore for neshlifovannogo the sample

In drawing 3.28 dependence of a difference of the temperatures registered on the thermoelectric couple and teplovizore is presented, at value of temperature on the thermoelectric couple. The sample was handled by nothing, gained as a result raspila a monocrystal. At exhibiting of coefficient of radiation on teplovizore 0,83 underload discrepancy of temperatures is observed to 350C. Since temperature 350C, and to temperature 80oC, the underload discrepancy of temperatures is observed at radiation coefficient in 0,85.

Processing of the effects gained during experiments has allowed to gain an overall picture of dependence of coefficient of radiation from temperature for surfaces of samples of a monocrystal of germanium with various parametres of a roughness (fig. 3.29).

Fig. 3.29. Dependence of coefficient of radiation of monocrystals of germanium from

Surface and temperature roughnesses

From diagrammes it is well visible, that the radiation coefficient decreases at temperature magnification. Proceeding from it the deduction has been drawn on lateral view change in connection with massoperenosom in pripoverhnostnom a material stratum on mikro and nanourovne.

For acknowledgement of the given deduction experiment according to influence of process of a heating on a roughness of a surface and on optical properties of the polished monocrystals of germanium has been executed.

Examinations were spent on the monocrystals of the germanium which has been grown up by an expedient Chohralsky in a direction {1H}, alloyed by antimony (a specific resistance r = 11-13 Ohm-sm; η conductivity-type; concentration elektricheski the active impurities 1,2? 1014см ' 3).

To fix these changes caused by a heating, in a mode of real time for the same site of the sample, in the optical interference profilometra NanoMap 1000WLI on a subject little table the heating device (fig. 3.30) has been placed.

About about

Fig. 3.30. The sample of germanium located on a heating device, placed in optical profilometra

Fig. 3.31. A site of a surface of the polished germanium before heating (at a room temperature 25oC) () and at temperature 65oC (). 2D - π po φπ∏ H before heating () and at temperature 65oC ()

The given procedure has allowed to depart from mathematical averaging on parametres of a roughness and to consider nanorazmernye the changes of a lateral view related to redistribution of a material in the course of a heating.

The fixed changes of a lateral view are presented on fig. 3.31. By the gained effects it is possible to draw a deduction, that in the course of a heating at redistribution of a material the surface lateral view takes a periodic form with disappearance of platforms, parallel a surface.

C the help of program SPIP 6.7.4. The analysis of a roughness of a surface has been carried out. Parametres concern standard SPIP Classic.

The obtained data are presented in tables 3.3 and 3.4. Filtrated the surface lateral view is matematicheski smoothed, and the curve of the relation of a material represents allocation on height.

Table 3.3 the lateral view Analysis at temperature 25oC

107


Table 3.4 the lateral view Analysis at temperature 65oC

108


For definition of influence of process of a heating on optical properties of a monocrystal of germanium the software featured in section 2.1 has been used.

The lateral views gained at various temperatures have been loaded into the program. In drawing 3.32 effects of modelling with a digitization step in 1 ° are presented. Corners, close to 90 °, correspond to reflexion, close to 270 ° correspond to a gear transmission. The extinction coefficient in models was equated to zero as us influence of change of a lateral view interested only.

Fig. 3.32. The calculated optical indicatrixes gained at temperature 25oC () and at temperature 65oC ()

Effects of examination specify in magnification of a share of diffuse dispersion from a surface because of changes of a lateral view and a roughness of the surface, caused by heating process. It, in turn, leads to change of coefficient of radiation of a surface and, as consequence, influences accuracy of definition of temperature with the help teplovizionnoj technicians.

The effects of experiments stated in the present section, allow to draw following deductions:

• At use teplovizorov for the purpose of measuring of temperature fields in monocrystal devices known values of coefficients of radiation are necessary, and at their lack carrying out of special examinations for concrete samples is required;

• the Microrelief and nanorelef surfaces, and also dependence of coefficient of radiation on temperature are the primary factors limiting accuracy of mapping of thermal fields with the help teplovizionnyh of cabinets;

• When the purpose is not peakly exact definition of terrain clearance values of temperature, in the Ik-defectoscopy it is possible to apply specially the underestimated coefficients of radiation to sensitivity pinch at detection of flaws and for magnification of contrast of patterns of their allocation in tested samples;

• Teplovizionnyj the method can be used for the control of parametres of a roughness, quality and homogeneity of a polish of optical devices by the analysis of heats pattern in the homogeneous thermal floor.

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A source: Tretjakov Sergey Andreevich. INFLUENCE of FLAWS of STRUCTURE And the MICRORELIEF of SURFACES ON OPTICAL HOMOGENEITY of MONOCRYSTALS. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver 2019. 2019

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