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the Phase analysis of thin films TSTS

Applying a method of diffraction of the reflected electrons udalost to fix two crystalline updatings in the generated thin films. Use of automated method DOE has allowed to spend comparison of the gained diffraction patterns (drawing 3.13) with the data which have been put in pawn in a computer database, and to choose peakly close patterns concerning monoclinic from each other monoclinic and tetragonal structures which parametres are given in tables 3.2 and 3.3.

In drawing 3.14 change of relation M/T in thin films is shown at a variation of pressure of working gas the Curve reflects a relation of the total of the areas occupied monoclinic (M) and tetragonal (T) with phases. It is visible, that growth of stability of a monoclinic phase was accompanied by reduction of pressure of working gas and the M-phase share increased almost twice - with 3,4 to 5,9, however the phase content perovskita thus decreased.

In drawings 3.15 and 3.16 images of a microstructure of a surface in the form of contrast of the diffraction strips and imposed on it by a card of two crystalline phases for the films gained at pressure of the worker are given

Gas 8 Pases and temperatures otzhiga films 600 C films.

Drawing 3.13 Characteristic diffraction pattern for monoclinic () and

Tetragonal () phases of thin film TSTS.

Table 3.2. Parametres of a lattice of the monoclinic phase TSTS, chosen from database ICSD for processing of effects DOE

Structure / parametres of a monoclinic phase And, And b, AND With, And β, degrees The number in

ICSD

References
Zr/Ti = 52/48 5.7103 5.6961 4.1378 90.50 90476 [143]
Zr/Ti = 54/46 5.7691 5.7427 4.0890 90.50 90479 [143]
Zr/Ti = 52/48 5.7129 5.7073 4.1436 90.20 90477 [143]
Zr/Ti = 52/48 5.722 5.7096 4.1365 90.50 92061 [144]

Table 3.3. Parametres of a lattice of the tetragonal phase TSTS, chosen from database ICSD for processing of effects DOE

Structure / parametres of a tetragonal phase And, And With, And The number in

ICSD

References
Zr/Ti = 52/48 4.0550 4.1098 90478 [143]
Zr/Ti = 52/48 4.0460 4.1394 92059 [144]
Zr/Ti = 52/48 4.0353 4.1312 90699 [145]

Drawing 3.14 Change of a relation of monoclinic and tetragonal phases in the thin films TSTS besieged at various pressure of working gas and otozhzhennyh on air at temperature 600 0C.

The drawing 3.15 Contrast of the diffraction strips gained for films, otozhzhennyh at 555 oC (), 560 oC (), 570 oC ()

81

Drawing 3.16 Contrast of the diffraction strips with the imposed card of the phases, gained for films, otozhzhennyh at 555 oC (), 560 oC (), 570 oC ()

The basic examinations by definition of a phase state of thin films TSTS were spent on the samples besieged at pressure of working gas of 8 Pases.

Dependences in drawing 3.16 show changes of relation M/T of phases in films depending on Totzh. In the first case otzhig it was spent in atmosphere of steams oksida lead at Тотж=555 ÷ 570 oC (drawing 3.17,), in the second case - on air at Тотж=580 ÷ 650 oC (drawing 3.17,). Data testify that with magnification Totzh the M-phase share in both cases decreased that speaks about importance of this parametre which change considerably affects a relation M - and T-phases in explored films.

Drawing 3.17 Change of a relation of monoclinic and tetragonal phases with temperature growth otzhiga in films TSTS in the thickness of 300 nanometers, 1000 nanometers.

For films in the thickness ≈ 1000 nanometers which have been grown up at pressure of working gas of 8 Pases and otozhzhennyh at 600 °s, have been spent measurings of a relation of the volumes, occupied monoclinic and tetragonal updatings of a ferroelectric phase with temperature growth. The magnification of temperature of samples led to essential reduction of a monoclinic phase which completely disappears at T> 180 oC (drawing 3.18). The gained effect will well be compounded with the phase diagramme presented in [62] and in drawing 1.4 and testifies to adequacy of used method DOE for definition of local symmetry of a ferroelectric phase.

The analysis of the gained effects allows to draw a deduction that the parents of change of a relation of monoclinic and tetragonal phases can

Drawing 3.18 Change of a relation of monoclinic and tetragonal phases at heating of samples by thickness of 1000 nanometers

To be change of a degree of element heterogeneity (atoms Zr and Ti) in a thin film, and also change of quantity of the mechanical voltages operating on a film from a substrate.

Element heterogeneity in allocation of atoms of the titan and zirconium is related to distinction of the energy (temperature) necessary for formation of a phase perovskita in PbZrO3 and PbT1O3 of which firm solutions are formed. In the first case, for tsirkonata lead, the temperature of crystallisation of the Re-phase makes ≈ 600 0C; in the second case, for titanata lead, it essentially less also makes ≈ 450 0C. If heterogeneity of allocation is observed on a thickness such thin films in the literature began to carry to a category «graded ferroelectrics» [48,146].

The parent of formation of heterogeneity in films PZT is caused by that inconvertible germs of the Re-phase will appear in those places of a thin film where local concentration of atoms Ti exceeds medial on film volume. Magnification Totzh will lead to magnification as to velocity of diffusion of atoms Zr and Ti, and to magnification of velocity of motion Pe-Py of a phase boundary. As magnification of velocity of a motion of interphasic boundary above velocity of diffusion of atoms Zr and Ti, it is possible to figure, that with growth Totzh a heterogeneity degree
Composition will decrease. If to figure, that stability of a monoclinic phase is spotted bolshej by homogeneity of a composition with magnification Totzh it is possible to expect magnification of its share. However the effects presented in drawing 3.17, testify to the return.

Considering the effects shown in drawing 3.17, and also that fact, that at reduction of pressure of working gas a M-phase share increases (drawing 3.7), it is possible to make the guess, that on stability of a monoclinic phase essential influence can render:

(1) mechanical voltages operating on a thin film from a substrate,

(2) reduction sverhstehiometricheskogo lead contents (drawing 3.7,),

(3) magnification of the relative content of atoms of the titan in a firm solution (drawing 3.7,).

According to [hh], quantity of the two-dimensional stretching mechanical voltages operating on thin film TSTS from a silicon substrate, depends on temperature at which there is a phase crystallisation perovskita. Drawing 3.19 thin film TSTS - a silicon substrate »(with an element relation of firm solution TSTS - Zr/Ti = 50/50) reflects effects of calculation of mechanical voltages in system« at two temperatures otzhiga - 580 and 650 0C. It is visible, that with growth Totzh quantity of stretching voltages increases approximately in 2 times.

Mechanical voltages change in the films besieged at various pressures of working gas (drawing 3.10). It is shown in rastreskivanii thin films as a result of activity of stretching voltages. Most likely, rastreskivanie the films besieged at 600 0C (drawing 3.10,) it is caused not only activity of stretching forces from a substrate, but also presence redundant oksida the lead which is settling down in mezhkristallitnyh layers of a film and on its interfaces. C reduction

85 pressures (and quantities of redundant lead in a view oksida) rastreskivanie are observed only in pirohlornoj to a phase surrounding islets of a phase perovskita. Drawing 3.19 Calculation of mechanical voltages in system «thin film TSTS - Si a substrate» at two temperatures otzhiga - 580 () and 650 0C ().

It is possible to figure, that perovskita in a film the relaxation of mechanical voltages occurs to reduction of a share of a phase for the account rastreskivanija phase fields pirohlora (drawing 3.10), thus Re-phase islets become less viced. It rastreskivanie, apparently, is caused by stronger odds in temperature coefficients of a linear dilatation of a phase pirohlora and silicon in comparison with a phase perovskita, and also smaller strength pirohlornoj structures.

Thus, the gained effects testify in favour of that major stability of a monoclinic phase is related to smaller quantity of voltages stretching a film.

Besides, it is impossible to exclude and influences of an element relation of atoms Zr and Ti on stability of the M-phase. The major share of the M-phase in experiments on a composition variation is observed in the films besieged at 2 Pases, where the content of atoms of the titan peak (drawing 3.7,) and equal ≈ 48 %. In experiments in which the temperature otzhiga changed, the major share of the M-phase was observed in the samples generated at rather low temperatures. In last samples it is supposed, that phase crystallisation perovskita occurred in the microfields enriched by the titan, a consequence

That the raised content of the M-phase can be explained also. These experiments testify in favour of that stability of the M-phase can be above in samples with the major content of the titan, and adjoining a phase boundary between monoclinic and tetragonal phases (drawing 3.6).

3.4

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A source: Kanarejkin Alexey Gennadevich. Ferroelectric properties nanostrukturirovannyh systems on a bottom tsirkonata-titanata lead. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. St.-Petersburg - 2018. 2018

More on topic the Phase analysis of thin films TSTS:

  1. Chapter 3. Effects of examinations of a phase state, structure and a composition of thin films TSTS
  2. temperature Influence otzhiga on a phase state, a microstructure and a composition of thin films TSTS
  3. Temperature measurings of the dielectric performances of thin films TSTS
  4. Change of properties of thin films TSTS at a variation of pressure of working gas
  5. Methods of reception of thin ferroelectric films TSTS
  6. 4.2 Examination of a self-polarised state and local polarisation of thin films TSTS by a method of power microscopy of the piezoelectric response.
  7. Chapter 4. Examinations of the dielectric, pyroelectric and piezoelectric properties of thin films TSTS
  8. thin films
  9. nuclear power microscopy for examination of morphology of surfaces of thin films
  10. Bystrozakalyonnye strips and thin films
  11. the Thermodynamic approach to a problem of the dimensional dependence of temperature of fusion of thin films
  12. 2.2 Research techniques of electrophysical performances of thin films
  13. 2.3 Structural examinations of thin films tsirkonata-titanata lead
  14. phase transitions pirohlor - perovskit I, perovskit I - perovskit II and their influence on electrophysical properties of films PZT (54∕46)
  15. Use of method DOE for the analysis of ferroelectric films
  16. Masons Michael Viktorovich. the ELECTRICAL CONDUCTIVITY And BARRIER EFFECTS In THIN FERROELECTRIC FILMS TSIRKONATA-TITANATA of LEAD. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2014, 2014
  17. the gas phase Analysis gazohromatograficheskim a method