<<
>>

THE OPERATION CONTENT

In introduction the urgency of a theme of examination is proved, are formulated the purpose and operation problems, scientific novelty, the theoretical and practical importance of the gained effects, the standings which are taken out on protection are presented.

1. In chapter 1 the review of the literature devoted to methods of manufacturing is presented, to studying of electrophysical properties and anomalies of ferroelectric performances of films TSTS. The special attention is given the operations devoted to use of a method of diffraction of reflected electrons (DOE) for the analysis of a microstructure of films TSTS.

C the publication moment in 1952 [3] firm solutions TSTS first to the phase diagramme it has undergone the considerable changes. According to [4] in the field of concentrations h = 0,46-0,48 the phase boundary (MFG), parting romboedricheskuju and tetragonal updatings is observed morfotropnaja

Ferroelectric phase where the extreme are observed

Electromechanical and

Piezoelectric performances. In the late nineties the last century - the beginning of this century a method of a X-ray diffractometry of the high resolution of volume ceramic samples existence in the transitive field of monoclinic updating of a phase (M-phases) was revealed, which at T> 300 To co-exists together with a tetragonal phase (T-phase) in narrow field of concentrations (rice 1) [1].

Lead of containing firm solutions was possible to find out a monoclinic phase and in a number of others. It is supposed, that anomalies of physical properties on MFG are immediately related to presence of a monoclinic phase [2]. Interrelation of the found out features of crystalline structure TSTS with it is abnormal high electrophysical performances in the field of MFG till now remains maloizuchennoj [5]. The problem related to a role of domain boundaries, magnification of density 7 is discussed


Which also is capable to lead to sharp magnification of the dielectric and electromechanical parametres [6-7]. In conclusion of the head the deduction becomes, that to examination of a phase state in thin-film firm solutions TSTS and accumulation of the observational effects in this direction representations about the nature of extreme properties in the field of MFG will allow to dilate application of new approaches.

In the second chapter the description of objects of examination, a method of formation of thin films TSTS and the observational toolkit applied in operation is given. The select of a composition of a target is proved.

Films TSTS were made in two stages. At first magnetronnogo pulverisations of a ceramic target on a "cold" substrate were besieged by method VCH stratums TSTS at a variation of pressure of working gas (80 % Ar + 20 % O2) within 2-8 Pases. Phase formation perovskita was carried out at otzhige films either on air, or in the furnace with the raised content of steams oksida lead at 530-650 °s. As the upper contact platforms the raised dust platinum electrodes were used.

Measurings of the dielectric performances, including, measurings volt-faradnyh (C-V) and the frequency dependences, were spent at the automated measuring stand including a measuring instrument of immittance Е7-20, a measuring little table, the circuit changer of a signal and the personal computer with the consecutive interface of standard RS-232.

The subject little table had the built in system of a heating and the temperature control that allowed to spend temperature measurings in the range of temperatures 20 - 500 °s.

Examination of a microstructure of thin films was carried out with use of raster-type electronic microscope Zeiss EVO-40. Two types of detectors were applied: the detector of secondary electrons and the detector neuprugootrazhennyh electrons with which help data about morphology and structure of a surface of films obtained. The method of an electron probe X-ray microanalysis which has been realised with the help energodispersionnogo spectrometer INCA X-Act, was applied to the analysis of an element composition of samples of a part raster-type electronic microscope.

Detector HKL Nordlys Nano was applied to diagnostics of crystalline structure by method DOE. For kartirovanija program AZtec, for processing of cards was used the complex of software products CHANNEL5 was used: Mambo, Tango. The characteristic diffraction card for TSTS films is given on fig. 2. The crystalline structure was spotted by a self-acting fashion - by comparison of the measured diffraction patterns with put in pawn in database ICSD and a select 8

The most suitable solution for each point of scanning. The medial angular diversion at indexing of the diffraction cards did not exceed 0,6 °. The size of fields kartirovanija got out proceeding from features of a microstructure and a state of a surface of a film. Besides method DOE X-ray diffractometer ДРОН-7 was applied to examination of crystalline structure TSTS of films.

Fig. 2 Characteristic diffraction pattern gained by method DOE for monoclinic and tetragonal phases of thin film TSTS.

Examinations of a surface and static domain structure in samples TSTS it was spent by a method of power microscopy of the piezoelectric response (mass-media) on scanning zondovoj Nanolaboratorii Ntegra Prima.

Fig. 3 REM the image sferolitovoj the structure of a thin film in the thickness of 300 nanometers generated at temperature otzhiga 560 °s.

In the third chapter effects of experimental researches of structure, a composition and the phase analysis of thin films TSTS are given. In the first paragraph data about a microstructure, morphology of a surface of the generated films are cited, representing plurality sferolitovyh the blocks which size varied in gamut IO-IOOmkm and was characterised by radially-beam structure (fig. 3). X-ray diffraction analysis data testified to polycrystalline character perovskitovoj structures with preferential -rostovoj orientation. Effects are featured
Examinations of an element composition depending on temperature otzhiga (Totzh), it is shown, that with temperature growth in films, otozhzhennyh on air, the redundant content oksida lead - from 9 % decreases at Тотж=580 0C to 3 % at 650 0C.

In the second paragraph effects of change of an element composition of thin films TSTS and the phase analysis depending on working pressure of a gas intermixture in process magnetronnogo pulverisations are presented.

On fig. 4 effects of a "thin" variation of a composition of besieged films PZT ≈ 1000 nanometers are presented by thickness at change of pressure of working gas from 2 to 8 Pases. Nuclear relation Ti ∕ (Zr + Ti) with growth of pressure of gas monotonously decreased (fig. 4,). The gamut of change of a composition did not exceed 2 %. The content of atoms of the lead, expressed in the form of relation Pb ∕ (Zr + Ti), changed considerably - approximately from 1,23 at 8 Pases to 0,93 at 2 Pases (fig. 4,).

Fig. 4 Change of an element relation of atoms a) Zr and Ti and) Pb and the totals (Zr+Ti) in besieged thin films TSTS with growth of pressure of working gas.

In process otzhiga reduction of the content of lead led to reduction of volume of a phase perovskita in the films besieged at low pressures of working gas (fig. 5) and phase localisations perovskita in separate perovskitovyh islets. C growth of pressure of a gas intermixture observed growth of number of islets of a phase perovskita and volume occupied with them. The full crystallisation of a phase perovskita in all volume to a film occurred at the pressure exceeding 6 Pases (fig. 5).

In the present operation of the parent of changes of an element composition in besieged films TSTS are considered from the point of view of change of requirements of a thermalization of atoms in plasma [9]. At the central arrangement of a substrate concerning a ring band of erosion of a target the magnification of pressure of working atmosphere leads to change of character of field of dispersion of atoms - from guided to diffuse which depends on an atomic weight of builders of a sprayed target. In

The above-stated gamut of pressures character of change of the diagramme of dispersion is most brightly shown for heavy atoms of lead, and in

Fig. 5 Change of the content of a share perovskita in the thin films TSTS besieged at a variation of pressure of working gas and otozhzhennyh on air at 600 °s.

Smaller degree - for easier atoms of zirconium and the titan.

In the third paragraph of the head effects of examination of a phase state of thin films TSTS are featured by a method of diffraction of the reflected electrons. Use

Automated method DOE has allowed to spend comparison of the gained diffraction patterns (fig. 2) with the data which have been put in pawn in a computer database, and to choose peakly close patterns concerning to a little differing from each other monoclinic (M) and

Tetragonal (T) to structures. On fig. 6 change of a relation of volumes M - and T-phases in thin films is shown at a variation of pressure of working gas. Effects show, that stability (share) of a monoclinic phase above in separate perovskitovyh islets, than in uniphase perovskitovoj to a film. At the same time, the M-phase content

Depends and on a film composition.

Fig. 6. 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 basic examinations by definition of a phase state of thin films TSTS depending on Totzh were spent on the samples besieged at pressure of working gas of 8 Pases. On fig. 7 changes of a relation of volumes M/T of phases in films depending on Totzh are shown. In the first case otzhig it was spent in atmosphere of steams oksida lead at Тотж=555 ÷ 570 oC (fig. 7,), in the second case - on air at Тотж=580 ÷ 650 oC (fig. 7,6). The presented data say that with magnification Totzh the M-phase share in films decreased. It testifies that Totzh is the important parametre which change considerably affects a relation M - and T-phases in explored films. One of the possible parents of such behaviour change of element heterogeneity on a thickness of thin films can be.

11

Fig. 7 Change of a relation of the volume occupied M - and T-phases depending on Totzh at otzhige in atmosphere of steams oksida lead and in aerial medium.

Fig. 8 Change of a relation of volumes M - and T-phases at change of temperature of the sample.

The diagramme presented on fig.

On fig. 8 dependence of a relation of the volumes, occupied M - and T-phases with growth of temperature of a film by thickness of 1000 nanometers besieged at pressure of working gas of 8 Pases and otozhzhennoj at 600 0C is given. The magnification of temperature of the sample leads to essential reduction of a monoclinic phase which completely disappears at T> 200 °s. The gained effect will well be compounded with phase 1 and testifies to adequacy of used method DOE for definition nanorazmernoj (local) symmetry of a ferroelectric phase.

In fourth paragraph 3 of the head observed datas of temperature dependences of an inductivity ε (T) (fig. 9,) and the dielectric losses of thin-film samples TSTS are given. The thickness of samples made 800 nanometers. Temperature Kjuri (≈ 380 0C) the explored samples 0C exceeded on 35-40 similar temperature, characteristic for their volume (ceramic) analogues. This odds testifies to essential action on thin films TSTS of stretching mechanical voltages from a silicon substrate.

In operation for identification M - and T-phases the method offered in operation [11] according to which it was possible to judge presence of this or that phase on change of declinations of temperature dependence of a return inductivity l ∕ε (T) (fig. 9,) is used.

Fig. 9 Temperature dependence of an inductivity () and its reciprocal value ().

Temperature M→T of phase transition was spotted as field of change of the declination scored on fig. 9, and corresponded to the transitive field 160-2IO0C, average which quantity (Tm.t) not strongly differing from the temperature spotted by method DOE.

In the fourth chapter effects of examinations of the dielectric, pyroelectric and piezoelectric properties of thin films TSTS are presented.

In first paragraph 4 of the head loops of the dielectric hysteresis (P-V) and volt-faradnye (C-V) performances of thin-film condenser structures on the basis of TSTS films otozhzhennyh in atmosphere of steams oksida lead are explored at 530-560 oC and on air at 580-650 °s which were studied in more details.

It is revealed, that character P-V and C-V curves changed after carrying out of measurings of temperature dependences of an inductivity when samples heated up to the temperatures exceeding temperature Kjuri. So, in the films generated at 580 °s, an internal field was maintained (fig. 10,), but in the strong fields there was symmetrization P-V (fig. 10,6) and C-V curves. In the films generated at 620 °s, the field vector has been oriented in a direction to the free surface segnetosloja (fig. 10, in,).

For acknowledgement of observable effect measurings of the pyroelectric response in a dynamic mode have been spent at an irradiation of samples prjamougolno by the modulated impulses with a wave length of 980 nanometers. The plus value pirotoka in the samples generated at Totzh = 580 °s, corresponding to orientation of a vector of polarisation in a direction to the inferior electrode, with growth Totzh was exchanged by the subzero value testifying about reorientatsii of a vector of polarisation, and quantity of subzero pirootklika increased (fig. 11) a little.

Fig. 10. Loops of the dielectric hysteresis, characteristic for films TSTS generated at Totzh = 580 oC (and,) and 620 oC (in,) after a heating of structures above temperature Kjuri in feeble and strong electric fields. Frequency of measuring -

1 kgts.

Fig. 1!.izmenenie signal directions pirootklika condenser structure Pt ∕∏ TC∕Pt depending on temperature otzhiga films TSTS

For an explanation

Observable effect

Are used it is some

The approaches, complementary each other. According to the first, developed in [12], formation of an internal field and a polarised state for lack of the upper electrode occurs in segnetoelektriyocheskom a stratum near to boundary radela film TSTS - the inferior electrode, and polarity is spotted by the cores

Charge carriers. The subsequent

otzhig above temperature Kjuri generated TSTS the condenser

Leads to redistribution of charges between upper and inferior interfaces ferroelectric TSTS the condenser.

The second approach will consist in the competitive mechanism of origin and phase growth perovskita on the upper and inferior interfaces of thin film TSTS and respective alteration of localisation redundant oksida lead [8]. And last is related to a role of the linear mechanical voltages operating from a substrate and giving either to a tension, or to squeezing of a thin film [12].

Examinations of a self-polarised state and local polarisation of thin films TSTS by a method of power microscopy of the piezoelectric response are carried out in second paragraph 4 of the head on atomno-power microscope Ntegra Prima (NT-MDT).

Piezoelectric measurings were spent on the films by thickness of 300 nanometers generated at Totzh = 530-560 °s. Polarisation was spent by a constant voltage yo 20 In on the area 5x5 a micron with polarity change with the middle of an explored site.

The analysis of the gained effects has shown, that the most inconvertible homopolar (self-polarised) state was observed in isolated perovskitovyh islets. It can be related that in system «a silicon substrate-lamina TSTS» which composition corresponds to field MFG, is treated to activity of forces of a tension from a substrate at the expense of distinction in temperature coefficients of a linear dilatation of stratum TSTS and a silicon substrate. Experiments have shown, that in two-phase system "pirohlor-perovskit" is observed rastreskivanie phases pirohlora as more "friable" and less strong. The partial relaxation of the mechanical voltages which are stretching perovskitovyj an islet, and maintenance bolshej parts of naturally homopolar state forming under the influence of a field of a volume charge, the stratum of self-polarisation generated near to the inferior electrode TSTS can be a consequence of it.

Under the influence of an exterior polarising electric field piezoelectric responses of various quantity were observed. In operation, including, the possible parents of these distinctions related to change of a microstructure, a composition are discussed with change of the content of redundant lead on a thickness of stratum TSTS, and also with change of requirements elektro diffusions of oxygen vacancies.

<< | >>
A source: Kanarejkin Alexey Gennadevich. FERROELECTRIC PROPERTIES NANOSTRUKTURIROVANNYH of SYSTEMS ON THE BASIS OF TSIRKONATA TITANATA LEAD. The dissertation AUTHOR'S ABSTRACT on competition of a scientific degree of the candidate of physical and mathematical sciences. St.-Petersburg - 2018. 2018

More on topic THE OPERATION CONTENT:

  1. THE OPERATION CONTENT
  2. THE OPERATION CONTENT
  3. THE OPERATION CONTENT
  4. THE OPERATION CONTENT
  5. THE OPERATION CONTENT
  6. THE OPERATION CONTENT
  7. THE BASIC CONTENT OF OPERATION
  8. THE BASIC CONTENT OF OPERATION
  9. THE BASIC CONTENT OF OPERATION
  10. THE BASIC CONTENT OF OPERATION
  11. THE BASIC CONTENT OF OPERATION
  12. THE BASIC CONTENT OF OPERATION
  13. THE OPERATION CONTENT