DETERMINATION OF OPTIMAL PARAMETERS TO RECEIPT THE SEMICONDUCTOR TAPES OF CdSe/ZnTe ON BASIS OF MATHEMATICAL MODEL

Worked out mathematical model of receipt the semiconductor tapes for comparison with experimental data got the method of molecular-radial epitaxation.

. Chart of device for the synthesis of tapes of CdSe and ZnTe in CCV: 1,2 are the evaporated compartments; 3,4 are heaters of walls; 5-7 are afterheaters; 8-10 are thermocouples; 11 is lining; 12 is a lining heater; 13 are stands; 14 are heater elements of vaporizer [1] Properties of thin-films substantially depend on the parameters of process of besieging: speeds of besieging, temperature of lining, remaining vacuum and others like that Speed of besieging is determined after a formula: where β is a coefficient of condensation, which takes into account the terms of condensation (frequency surfaces, temperature), x -const, that depended on the form of vaporizer.
Speed of evaporation in id est amount of matter [2,3], evaporated for one second from unit of area of surface of vaporizer, calculates in obedience to the formula of Hertz-Knudsen [4] but looks like: where Р s is pressure of pair of matter. In times of t evaporation an amount of the evaporated matter is from the vaporizer of radius of r: σ = wπr 2 t.
(3) On condition that all atoms of evaporant condense on lining a desorption is absent, it is possible to consider that σ= G, where G is mass of the got tape.
The thickness of tape can be certain from correlation: where m is mass of evaporant, t is time of evaporation. Thus under a thickness understand such thickness, which the layer of matter, equipartition for surfaces subspoon would have with the closeness of this matter. In an order to take into account the unevenness of distribution of tape for the surfaces of lining it is necessary to enter the coefficient of proportion of Z: ) = ( +, - where h is distance from the center of lining to the view point, L is distance from a vaporizer to the center of lining.
Then finally will have a formula: Expression for high speed of evaporation (2) was got Lengmur [4] from experiments answers evaporation from free-form, id est situations of not "returning" of the evaporated particles are on the surface of lining. Such evaporation is named lengmured [4]. By a key variable which influences there is a temperature on speed, as she is strong influence on pressure saturated pair.
(7) At causing of tapes by the method of evaporation a matter must evaporate in the molecular mode ( fig.1), an atomic (often as "molecular") bunch is here created, and his particles move from a vaporizer to the subspoon rectilineal, without collisions. In obedience to these terms and on the basis of kinetic theory of gases it is possible to get next dependence: C ≈ 5 • 10 E / (66. 6. 8).
Then according to initial data will get a value 3near 1-7 Pascal. Putting finding to (7) where a -is distance from a vaporizer to the looks point, L is distance from a vaporizer to the center of lining. For determination of thickness of d in the set point of subspoon it is necessary look to examine evaporation from all elements of ring [6]. The angular co-ordinates of element of vaporizer are determined by a corner ά, and for the stowage of holding from every element it is necessary to integrate for ά from 0 to 2π. J = C + ' + ℎ + 2ℎ'cos (P), (11) where h is distance from the center of lining to the looks point, r is a radius of ring of vaporizer.
At calculations assumptions are done in relation to descriptions of evaporation from the separate elements of vaporizer. HollandandShtekelmaher conducted a calculation for a "ring which consists of point or superficial vaporizers". Integration for ά equalizations (9) and (10) taking into account equality (11) gives for a size d expression: Comparing expressions (12) and (6) can get expression for time of condensate t: Time of evaporation folds from 5 с to a few minutes, depending on mass of condensate matter. Coming from finding can define the optimal parameters of receipt of semiconductor tapes. Pressure of pair of matter 3 it is better to do a permanent size (in this research 5 pascal), id est distance from a vaporizer to lining always unchanging. Also from these data swims out, that and a temperature of evaporation is a permanent size.
Knowing what thickness of semiconductor tape it is necessary condensate on lining it is possible from a formula (12) to expect mass of evaporant. Time of evaporation of t settles accounts after a formula (13) for every found mass of evaporant.

Conclusions
The worked out mathematical model provides high enough exactness of approximation and flexibility to the change of terms of receipt.
For the brought objects over it is got: pressure steam evaporant -5 Pascal optimal temperature of evaporation -650 К, optimal value of distance from a vaporizer to lining -a 100 mm a mathematical model is created for the calculation of thickness of semiconductor tape and time to the necessity for her causing on lining. Research of receipt of tapes of different thickness is conducted, at it data of experiment with high exactness of near with data of theory.