Structural and electrical properties of SOL-GEL processed PLZT thin films

STRUCTURAL AND ELECTRICAL PROPERTIES OF SOL-GEL PROCESSED PLZT THIN FILMS

勿

CHARlAR VIJAYARAGHAVAN M.

DEPARTMENT OF PHYsIcs

Sul>mittcd

iflル 1/ihnent ofthe re興irements oftiie degree qf DOCTOR OF PHILOSOPHY

to

le

INDIAN INSTITUTE OF TECHNOLOGY, DELHI

DECEMBER 1998

CERTIFICATE

This is to certify that the thesis entitled 'STRUCTURAL AND ELECTRICAL PROPERTIES OF SOL-GEL PROCESSED PLZT THIN FILMS' being submitted by Chariar Vtjayaraghavan M. to the Department of Physics, Indian Institute of Technology, I)elhi foi

the awai

d of the Doctor of Philosophy is a recoi

d of bonafide research carried out by him. He has worked under our guidance and supervision, and has t.

ilfillcd the req

ii'

ements for the submission of this thesis, which to our knowledge has reached the requisite standard.

rhc results contained herein have not been submitted in part or

11 to any other

Ifl ive

sity ci

institution

I. award of any degree or diploma.

え＿^r

■ (. If

(R.G. Mendiratta) Professor

Department of Physics IlT, Hauz Khas

New Delhi

110016 (' ！、， ^{C. G()el)}

1)1・（)1七5501,

D 叩 a1'tm 叩 t ば Pllysics IIT,Hauz Khas

New Delhi-110 016

Ded 】 cated to

Vidwan Sri U.Ve,Srinivasacharya

ACKNOWLEDGMENTS

I convey my heart

It gratitude to Professor.T.C. Goe! and Professoi

RG. Mendiratta for introducing nie to i

ese ai

h in electi

oceramics. It was Ju!y 1993 and it took us quite a while to dcci

ie on an intei

esting research pi

oblem in materials science with applications in SclflicOIlductOl

ind

isti

y which wc could addi

ess with oui

cxperience of ceramics pi-ocessing. Pi'o1

SSOrS Guet and v1cndii

atta have been nlost undci-standing and their s

ij) poi

li ve yet noii-i nterfci

ing attitude to my reseai

h woi

k is something I chei-ished.

The gentic suggestions and encouragement provided by Prof. P.K.C. Pillai during CIi SC

iSSiOflS WC

always a great so

II

e of motivation for

me. To help out with the teething problems I faced in the initial stages of the so! preparation and electiical characteization, Di

A.K. Tt

ipathi was always there. His contribution to this work is immense. Anul (3ovindan was the one reliable person ever ready to help in any kind of hardware problem tlmat I fa

(j ifl nly expei

i mllental voi

k. I am thankful to the Ficad, Department of Physics for PI

ovidingl' aci li lies foi

cal

1

ying out this work and to the various research groups of the clepat

tnent for theii

assistance fi

om time to time. To my colleagues in the laboratory, Di

i1.D . Sharma, Dr.Anjali Verma, Dr.Ajai Carg, Anoop Yadav and Mohan Sh

ma, I am thlankful for all the discussions anc[ inputs without which work wouId not have reached this iihapc. I ai-n thankful to the technical sia

of the Department of Physics and the Central Workshop for the excellent technical support provided by them. I am grateful to the Council of Scientific and Industrial Research (CSrn) for supporting part of this work by awarding me a Senior Research Fellowship.

The results of the fcrroelectric studies would have looked very different without the assistance of Dr. Suhhasish l3asu Majumder and Atanu Saha <ACMS, HT-K). I am thankful to them foi

being wonde

i hosts duiing my visits to Kanpur.

J shall always cherish the memories of the time spent in Shivalik in the company of

Satish Balachandra, Sushil Fulzele, R.V. Ranganath, Sharat Chandra and Nidhi Nath. For

the precious support that only Partha seemed to be able to provide, I shall ever remain

gi

ateful. To Anurag Gupta, Vivek Sh

la, Praveen Nahar and Nitin Dahiya (all of Nature

Club), I am grateful for being great friends and co-conspirators in vatous activities during

OLlI' stay in IITD. Many a beautiful moment was spent in the company of Yogesh Choudhary, Manu Mahavar, Kirti Jamn, Bharat Sardana, Sandeep Kumar, Manoj Gupta and S

U

endran.

Varghese, Bob, Sui

esh Bhat and R

i Thomas never said no to my repeated requests for various odds and ends. To Mahaveer Juin, T. Rajagopalan and Oommen Vargties

)f Fhin Fil m Laboratory I anl grateful for helping with x-ray st

idles, thickness Ifl

15

1

i'iiefllS and inctallization. Special thanks to Dr. Shahani (IViDIT Lab) for providing IflO with computing facilities iIi the last phase of submission.

j was fortunate to h1ave had the support of umpteen friends within and without TITI) who have been compassionate during this seemingly never-ending process of experimental W01'k and thlesis completion. Li

would have been dull 'vithout the many discussions and ui

gunlents with Pi

of. Swaminathan, Ai

avind and Tcnzin. My de

gratitude to Saisudha ari

I Shanib

i Pi

asad, who hosted me, took great care of me during the last stages of experimental work and kept me going in the writing stage. For being wonderful friends and keeping my interest in work alive when everything seemed di

icult, I am grateful to Radhika, Sandeep, Navjyoti und Anuradha. Last but iot the least, but for the quiet support that I received frolfi my famnily, this work would not have reached its completion.

《 七

(Charlar Vijayaraghavan M)

ui

ABSTRACT OF THE THESIS

STRUCTURAL AND ELECTRICAL PROPERTIES OF SOL-GEL PROCESSED PLZT THIN FILMS

CitARIA1 VIJAYARAGHAVAN M DEPARTMENT OF Pitvsics

INDIAN 1NS'I・ITUTE OF TECHNOLOGY, DiらLIII Nilw 1)IこLI1I-11OO16 INDIA.

AlとF『いeleじInC iilatei'ial is one, which has two or mo比orientational states in thle absence of an external electi・ic hield, and the state could be switched from one to the othel・by means of an externally applied electric fleld. Ferroelectric materials exhibit reversible spontaneous polarization, high dielectric perInittivitics and show strong piezoelectric, pyroelectric and electro-optic effects. While there are Ii1ltitttiOflS(()the applications of 紀ri・叩lectric maにrials in bulk form owing to the high operating voltages reqしlil.C(l, advancじs in1 thin-fi1nl ぬbrication technology aLongwitb parallel developments in i nlegnitc(l-c ircui ti・y and ebceti・o-optic technologies have led to an explosion of intel・est in tbc ferr（光lecti・ie thin film technology area. The unique properties ofたrroelectric materials, combined with th巳desigii flexibility and miniaturization offered by thin五lin geometries have fueled this explosion.

Since the early 1970's, the enormous potential of たri・oelectric thin flims for device applications hus been recognised. Thin films of たαoclectric devices are being considered for aD!1 ictしtions in numerous electronic and electi・o -optic devices ranging from non-volatile semiconductor memories, large-scale electro-optic applications such as optical waveguide devices und spatial light modulators, switching capacitors for integrated circuitry, SAW devices, pyroelectric devices and imaging sensors. Ferroelectric thin films are especially attractive owing to the potential for monolithic integration with electronic and optoelectronic device systems. In addition, thin film materials offer the potential for increased speeds, reduced voltages and enhanced effleicncics. Non-volatile memories have additional advantages of high density and radiation hardness among others.

Over the last five years, non-volatile memories are occupying an ever-increasing share of the memory market. The majority of present-day non-volatile memories, the most versatile of which is the EEPROM, have relatively large cell sizes and need high voltages for writing. Compared with the older non-volatile memories，琵ロoelectric random access memories (FERAMs) offer t畑advantage of very fast access times (for both reading and writing), low-voltage operation and a very good write

lv

endurance. One of the additional advantages of these materials in comparison to EEPROMs is their high degree of radiation hardness. As a result, such ferroelectric memories are potentially attractive for しise both in military systems, where their robustness and high speed (>1O3 fastei－肥ad write times than magiletic bubble) are attractive and in civilian satellite applications where the device must repetitively PISS thlrough the Van Allen belt.

PZ' r i5 ()flC of the niost highly investigated ferroelecti・ie materials both in thin filn and powdci・ Ibl・Iris, owing to ils superioi・fei・r叫lectt・ic pmpertics, One of the major applications of films of the P刀 1なmiily is in noiトVOlItilCたrroelectric memories. These films arc found to degrade with i・epeated read-

write cycles. Overcoming the fatigue and degradation behaviour has been a challenging problem from tulじ point of viじw of tile applications in non-volatile memories. Several rare earth additives have been mlleo叩orated in PZT to tailor the material to the needs of the application in question. In particulai・，

laiithanuin modi石ed lead zu1・conato titariate (PL刀）thin films having perovskite structure are of interest in applications including non-volatile memories, electro-optie modulators, microactuators and inli・aied sじti SOI・s.

' rl]e utilisation of ferroelectric thin丘Irns for electronic and electro-optie applications has been limited by limitations of deposition processes for device-quality ferroelectric thin-flims. However, 1・eceut advances in thin ffilm d叩osition technology, especially in the areas of sol-gel technology and nユetal organic chemical vopoしir deposition (MOCVD) hlave generated significant excitement within the electroecramics community. The excitement over sol-gel thin-ffiixn teclmology isにlated to its pI・omise toward fleeting the quality比qしIirements for device applications alongwith the ease of fabrication. In essence, the p rOCQSS involves the dissolution of the required metal ions, either as alkoxides or other mnetal-organic salts in a suitable alcoholic solvent, or as m11o恰anic salts in an aqueous solvent to form a sci. This is followed by the gelation step in which the fluid sol is transformed to a semi-rigid gel. The process can proceed by a number of different routes, resulting in either polymeric or colloidal 即ls, depending upon the particular system. Owing to the intimacy of mixing the constituents and to the じxtrcme reactivity of the dried gel, the crystallisation stage may occur at te叩ei・atures several hundred degrees lowet・than those required for traditional mixed oxide processing. These reduced te叩eratu肥s could enable the direct integration of ceramic components with se血conductor devices, and other substrate materials, as well as the fabrication of unique material combinations with phase assemblages and novel properties.

For incorporating PZT and rare ea仕h modi丘ed PZT in ferroelectric applications, it is desirable to obtain films in the pure perovski把phase, because only the nonくentrosymmetric perovski加phase is

felToelectric. A centi・o-syrnmeti・ic paraelec(iic phase exhibiting the pyrochiore structしIl・e, which clegradじs t he pl・opei・ties of intei・est, has also been reported to exist in varying amounts in PZT・

The o可ectives of the present work therefore were to optimise the process pai・arneters to pl・epal・e homogeneous, device quality films of PZT and PL安in the pci・ovskite phase by soL-ge1 processing and to study the phase foi・niation behaviour, microstructure, electi・ical and optica' plひperlies. The work has been desci・ibed in石ve chapters.

(:Iiai)ter One pi・（)V1CICS a brief introdしictioii to ferroelectric matci・lais and (lie potential i1PPlications Of- Iと1・roじ1じctric (hin flhns. 'flic pi・epat・ation of PZT and 凡ZT thin flims by sol-gel processing is i・巳viewed. Conimonly usじcl たi-r叩lectric thin flim fabrication techniques such as spしittering, lasci・ablation and chemical vapour deposition have been discussed and co卿ared with the sol-gel process. Major achievemnents by research groups working in the area of preparation of 危i-1・oclectric thin 丘Ims have heen highlighted. Some of the outstanding issues that have not been addressed to or those that need further research have been outlined. Accordingly, problems for the pi・じsent stしicly have heじn iclenti丘cd.

Chapter i"vo deals with details of the experimental procedure used for the preparation of 1)z,.I, and PL刀1 丘lins and the vlしniotis characterization techniques that have been used to obtain information about ilie structure and properties of the deposited 五Ims. The procedu化s used in the electrical and optical studies have also been discussed. This chapter also deals with the optimisation of the various process deposition parameters to 比producibly prepare smooth, ci・ack-free and 11()n1ogcneous thin {ulnls. The tcillperatしii・じ ranges for solvent evaporation, remnoval of organics and crysiallisation were determined ffloill infrared spectroscopy (IR), thermogravimetric analysis (TGA) and x-ray diffraction (XRD). Based on the results of these studies, heat treatment schedule for the flim was devised. The effects of molar concentration of the sol, spin speed and repeatect coating on the thickness and quality of the flims have also been studied. The optimum sol concentration for obtaining sruiooth crack-free films was found to be 0.2 Mルto 0.4八VL. A spin speed of 3000印m and a spinning Urne of 20 s were found to be optimum for preparation of thicker films with smooth surface. A heat treatment temperature of400. C for 20 min. was found to be optimal to remove organics and obtain an amorphous flim.

Chapter Three contains results about the phase formation, microstructural studies and optical characterization in PZT and PLZT丘lms. For these studies, three compositions of PZT and three compositions of PL加have been chosen. The compositions of PZT chosen for investigation were 65/35, 40/60 and 30/70 PZT, The compositions of PLZT chosen t'or investigation were slim

v'

hysteresis ioop compositions, 8/65/35, 15/40/60 and 18/30/70 PLZT. A thin interlayer of PbTiO3 (400A) has been used prior to depositing PZT and PLZT thin flirns on Corning 7059, quartz and platinum substrates. The interlayer of PbTiO3 was found to facilitate crystallisation in the pじrovskite phase at a 1owel・temperature. Two heat treatment schedules have been used, normal heat treatment (NHT) and rapid heat treatment (RHT). The phase formation behaviour of PLZT Films has been foしmd to he signi丘canhly different from that of the bulk. PLZT films ful・st 面rm in au aniorphoしus pluuse and laLer crystallise either into pyrochlouで Or perovskite structure depending on the substrate, coniposition and heat treatment schedule. Perovskite phase formation is favoured 'vhen tule substrate is crystalline and inert, the ZiTfi ratio is small and Pb concentration is large.

Complete perovskite phase formation in 8/65/35 PLZT, 15/40/60 PLZT and 18/30/70 PLZT 丘Ims lias been achieved at 650. C, 600- C and 525、 C respectively. In flims, the arno叩bous phase is likely to transform to a pyroclilore phase first. The subsequent transformation to perovskite depends on factors sしudli as natu化of the substi・ate, fllm thickness, composition and temperature.

、1、！1じ initial fo〕l・Ination of pyu・ochlou・e phase at low annealing temperatures has been attributed to the higher acti vation energy harrieu・fou・the amorphous to perovskite transformation. The difficulty in the formation() f perovskite phase is related to the conditions that promote lead loss during the film 1)1・cparutiou1. Perovskite formation is found to be丘Ivoured in flirns with high Ti content because in these films, Pb is more effectively hound. The perovskite phase also forms easily on substrates such as sapphire, plati1liuill and NaCI.

Thle microstructuu・e of PZT and PLZT thin films displays sorne typicalたatuu・es. Two of these au・じ tbc extreme fine grain size of the pyrochiore phase and the rosette-like structu肥of the perovskite phase. The perovskite phase initially displays grain like featu化s・These grains are not single crystals; each grain consists ofciystallites, which were too fine to be resolved by SEM. With iuicreasiulg auinealing time, the grains developed a radiating line pattern characteristic of the spherulitic sti・uctuu・e. Further annealing leads to growth of crystallite within the grains. However, CVeII prolonged annealing for 3 hrs. at 650oC did not lead to increase in grain size beyond O.2lim.

La doping enhanced the growth of the perovskite crystallites. For usual heat treatment times, the perovskite crystallites within the grains were beyond the resolution of SEM. However in PLZT films subjected to rapid heat treatment, subinicron sized perovskite crystallites of uniform grain size were readily observed.

Optical studies have also been performed on PZT and PLZT thin films・The optical properties were investigated using both reflection and transmission spectra in the wavelength range 200 mn to

VII

go() tim. The refractive index (n), extinction coefficient (k) and thickness (d) of the films were deici・mined from the ti・ansmission spectra. Thickness of the f!m obtained from the interference fringes agreed well with those obtained from other methods. The appearance of interference fringes itself is an indication of the thickness uniformity of the flim. The following conclusions were di・awn fi・0111 the optical stしidies. The i・^eft・active indices of the thin films are somewhat lower than tlia( of' the t〕しilk. This has been atti・ibuted to the stresses and the residual poi・osity in the films. The lOW value of extinction coeflicients indicates the excellent surface homogeneity of the films. The jiacking fr・action shows sonic increase in the case of PLZT films and is atti・ibuted to the imp!・oved densi ficalion in these filais.

Chapter Four deals with the study of the electrical properties of P71' and PL灯 ffilms. The electrical behaviour of these films is known to depend on the presence of different phases and dopants, the grain size and grain size distribution and the nature of the device structure used for investigation of the d」ecir・ical pr・（M)d1、tiCS. The dielecti・Ic properties of the thin flims wei・e charac texうsed in terms of the disper・^Sioll(）【－ the dielectric constant (er) and loss tangent (la,：の values. The room temperatu化 diじlectt"ic COflSUlfltS 恥r the thl・ee P i:ー窟compositions, viz. Sf65135, 15/40/60 and 18/30/70 were found to he 1200, 950 and 6（冷 respectively. In particular films that have been subjected to rapid heat treatment exhibi回superior insulating properties than丘iras p肥pa肥d with normal heat t化atment. The ferroelectric prop町“^{ties a}肥^charact町ised from the P-E hys肥resis loop characteristics, The PLZT ffilms litve Cxhit)itCd slim11 hyste肥sis loops. The lower coercive field as compared to PZT flims bas 恥en attributed tc the incorporation ofLa, wliich results in reduction of stress in PLZT films. The ac and dc degradation characteristics of the flims were studied in terms of the fatigue and current-voltage characteristics. As compared to the PZT flims, the PLZT films exhibit superior魚tigue resistance.

From the studies carried out, it can be concluded that PZT and PLZT films with high dielectric constant, good 肥rroelectric and endurance properties could be prepared by sol-gel processing・ Further, it is concluded that normal heat-treated丘Iras have higher density of Ieたet regions and large number of pal比d Pb and O vacancies forming dipoles. Rapid heat-treated films exhlibit加比^er nc properties due to the absence of the above and due to the increased carrier concentration. These studies demonstrate the improvements in ferroelectric properties arising out of controlled processing conditions and La substitution. Processing conditions can control phase formation, microstructure, possible existence of interfacial layers and the electrical conductivity. The studies highlight the centrality of defects and dipoles in explaining the ac and dc degradation characteristics.

vilt

Chapter Five summarises the results of this study, highlights the important conclusions and suggests possible scope for future work. Films deposited on Corning 7059 glass, quartz and Si had a strong tendency to Crystallise in the pyrochiore phase. The formation of the pyrochiore phase on these sしtbstrates is attributed to the loss of lead by (i) diffusion into the substi・ate and(ii) reaCtion with the sしil,strate. 'Vith increasing石lm thickness, perovskite phase foimation was promoted. Use of a seeding layじr oU PbTiO3 also promotes pet・ovskite forrnation on these sしibsti・ates by pr・ovidirig sites 島1・

PCI・ovskite nしLClCaliOIl. On sしibsti・ates such as Pt, alumina, NaCI and sapphire. pじrovskite phase to)t・illiltion 'vas favoured. Rapid hじat tiでatment was found to be more useful than normal heat treatment to obtain single phase perovskite thin tulnis of P刀arid PLZT. Films subjected to normal heat treatment exhibit dispet・sion in dielectric properties, poor肥sistance to fatigue and superior resistance to dc degradation. ln contrast，石Ims su可ected to rapid heat treatment exhibited little or no dispersion in tite dielectric pi・opertics. better resistance to長ltigue and poor dc degradation chai・acleristics. It lias been suggested that noi・trial heat-treated丘lms have mo肥deたcL iもgioris and large numhei・of pai肥d Pb and ()viしCanCieS forming dipoles. Controlled substitution of Pb in P刀thin films by La has 化suited in inlproved ferroelectric propeiies and resistance to fatigue. The initial formation of pyrochlore phase at low annealing temperatures could he attributed to the higher activation energy barrier for the am11orphous to perovskite transformation. The di伍culty in the formation of perovskite phase is related io the higher transforinution hurrier foi・the perovskite phase as compared to that of the pyt・ochio肥 phlase. Pet・（)VSkitC tot・nittiOii in filins with high Ti content is 伍voured, Cot叩ositions I・ich in Ti ctystallisc in the perovskite pllase at lowet・heat treatiilent temperatures. Complete ci・ystallisation in the p巳rovskite phase takes place化r the three PL刀compositions viz., 8/65/35, 15月0/60 and 18/30/70 at 650OC, 6(X)oC and 425QC respectively. The inicrostructures of PZT and PLZT thin fin1is display some typicalたatures. Two of these are the extreme fln巳 grain size of the pyrochio肥phase and the rosette- like structure of the perovskite phase. La doping accelerates the b肥akup of the grain-like sti・uctut・e and proiilotes the growth of thle perovskite crystallites. The refractive indices of the films have been found tO be somewhat lower than that of the bulk. This bas been attributed to the stresses and the residual porosity in the fllms. The low value of extinction coefficients indicates the excellent surface homogeneity of the 石ims・The packing fraction shows some increase in the PLZI' ffilms and is attributed to the improved densiffication in these films.

Recommendations for further work have been made. Attempts should be made to further reduce the crystallisation temperature for perovskite formation in thin films for ease of integration with Si-technology. To achieve this, the use of self-assembled monolayers (SAMs) might also be

ix

aflenipted. Detailed microstructui・e stしtdies with SEM, AFM etc. are desirable to integrate these films into memories, microelectrornechanical sensors (MEMS) and other devices. The study of electrical properties of thin fei・roelectric films needs coi・「elation with the microstructure investigations. ESCA/AES studies could lead to better understanding of the mechanisms of Pb dil'l、usion and the dyuaillics at the flim substrate interface. MIS studies of PLZT on Si would be an im11portant aldition toしinderstand tule electi・ical properties of the thin films. Stしidies of the phase loi・lrulti()rl hehavk）し11・in ainbients sしich as 02, Ar and N2 may lead to films with superior strしictural aiul electrical pi・（)1〕じ1・ries.

d. 「 1 1 つ1 一6 1 7 9 1 1つ一 2 つ

1

27 27

0八 ハU lーA つ】 マJ 一つ

TABLE OF CONTENTS

(、.r[i【 'icatc

Ac kno'vlcdgcLuen is A hstrac t

'Fai)」じ 01" ("oii1ciits List()1' Figures List of『 Fables IJisi o1" Ikiblicatioi1s

CI IA PTER oNE INTRODUCTION

i .2 凡1・1・oeleciric rnatcl・jais: a h」・jef bistoi・jcal summary I . 3 Siriictui・e and pt・oPel・ties of PZT eじrarnics

F4 Fer・1・oclectric thin films

1.4.1 Pci・1・oclecii・ic 行！ITIS loI・non-voiati1c mernot・ios

」.4.2 TIliil film deposition techniques 1.5 Liter・ator・e review of PZT arid PLZT thin filins 1.C) SOI・gel pi・Ocess

i .6, 1 Drying of gel 1.6.2 Float ti・catinじrit 1.7 Sol-gじ1 lI.ocessiIig of i）ひtlliii filins

i .8 Statement of the Problem: Objectives of the present work Reたfelices

CILAPTER TWo) PREPARATION AND CHARACTERIZATION

PROCEDURES

1よ つー つ一 2

Thlin film deposition by the sol-gel process 2.1.i Chemistry of the sol-gel process 2. 1.2 Precursor materials

2.1.3 Sol preparation

2. 1.4 Preparation of the substrate 2. 1.5 Film deposition: Spin coating

2. 1.6 Thermal analysis and heat treatment of fllms Characterization of thin films

l Il I V XI X V X V t 11 XIX

QU 00 つ一（コ】『一一り一6 一0 へつ （つ44444 4

2.2.1

X-Ray diffraction study

Scanning electron microscopy

Uy-VIS spectrophotometry

Thickness measurement

Elじctrical measしII・eme rits

Sarnple con行gしirat ion Sampiじ holdei・

l)ielectric measurements c-v incasしli・ements

Hystet・じsis ioop inじasui・じ'Tiじilt Mじastirement of丘i.tiguc

M cas ui・ement of leakage curi・ent l)cposition process: Sol-gel spill coating

Optimisation of process parameters

2.5.1 E日もCt of molar concentration 2.5.2 E価Ct of spin speed

2.5.3 Effect ofmuifilpic coating 2.5.4 JR spectroscopy

1えc」bl・erices

ChIAPTER THREE RESULTS AN!) DISCUSSION: PI-tASE FORMATION 13 EFIA VIO UR

3.1 13ししekground 69

3.2 Pyrochloi・C rind perovskite foi・ination in PZT arid PLZT huirns: 70 Litei・attn・e'・eports

3,2.1 Phase formation in PZT flims deposited by 70 physical vapour deposition

3.2.2 Phase formation in PZT films deposited by 70 chemical deposition methods

3.3 Results of phase formation behaviour 74

3.3.1 E脆Ct of various parameters on phase 'formation in 74 PZT thin flims

(a) Thickness effect 74

(b) Substrate effect 76

3.3.2 Effect of various parameters on phase formation in 78 PLZT thin films

(a) Effect of substrate 78

(b) Effect of seeding layer 79

(e) Effect of heat treatment 79

(cl) Effect of composition 82

うつ 1什 一『一 つ」 つ】 つ一 1 つ一「j J4 ぐ．) 乙い ワ1 （コ （コ〔コ 「つ 「j コJ 「つ つーつーつーつーつーつ一2

4849

49 51 51

57 58 60 62 6262

68

3.4 I)iscしission: Phase fol・mation behaviour

(a) Pb deficiency/loss (b) Zr/Ti content

(c) Natし11・e of the substrate (d) Film stresses

3.5 Siilllnliii・y and Conclusioiis: Phtしse formation behavioしIl・

3.6 Miei・（うsti・uc tしiiでof PZF and nlodified PZT thin flims: Background 3.7 Iこesし1Its〔）」、 lUie i,osti・ut: tui・e stしidics

(a) E!恥et of substrate (h) E脆et of seeding layer

(e) Effect of heat treatment schedule (d) Effect of composition

3.8 Microsti・uctui・C development: Sumniary and conclusions 3.9 Optical pt・opertics of en・oelectric thlin films: Backgi・ound

3.9, 1 Optical constants evaluation 3.1() ()1)t ical clxii・acte】・ization : Results and discussion 3. 1 1 Suiiltilit・y of“叩tieni stしidles

Re ferences

CHAPTER FOUR RESULTS AND DISCUSSION: ELECrIIRICAL CEIARA CTERIZATION

4.1 Dackgi・（）しind

4.2 Electrical properties ofPZT thin flims: A brief review 4.3 Experimental method

4.4 Results of electrical studies

4.4. 1 Dielectric properties 4.4.2 c-v loop characteristics

4.4.3 Current-Voltage (I-V) characteristics 4.4,4 Hysteresis characteristics

4.4.5 Fatigue characteristics 4.5 Electrical properties: Discussion

(a) Effect of heat treatment/Phase formation (b) Effect of La substitution

4.6 Electrical properties: Summary and conclusions References

Lリ 6001 2 4 【ノ 71 「IOJCノ nU ハリ ハU O 「U n on n凸 aノ0一0ノ 9 (）ノ 0ノ 0ノ0ノ0ノ0ノ 1

1 1 1 1 1 1 つ一 ロU CO qノ0ノ0ノ（コ （コ ワ1 1

11 11よ 11 1 つ」つ一（コ【『」 「つ

■ ーユ 11→ IA 11 11 111 一eel l上 11 山ーよ

143 145

CH A.Pi'ER FIVE SUMMARY, CONCLUSIONS AND

RECOMMENDATIONS FOR FURTHER RESEARCH

5.1 sし」mrnai-y 147

5.2 Conclusions 148

5.3 Recommendations for・furthei・1・esearch 15()