Journal of Physics Conference Series

OPEN ACCESS

Pulsed laser deposition and characterization of(BiFeO3)07-(PbTiO3)03 thin films

To cite this article M A Khan et al 2006 J Phys Conf Ser 26 069

View the article online for updates and enhancements

Related contentFormation of Polysilicon Films by CatalyticChemical Vapor Deposition (cat-CVD)MethodHideki Matsumura

-

Substrate temperature effects on thestructure and properties of ZnMnO filmsprepared by pulsed laser depositionH Riascos J S Duque and S Orozco

-

Pulsed laser deposition of carbonnanodotsG Muntildeoz P Homm F Guzmaacuten et al

-

Recent citationsRut Rivera and A Safari-

Multiferroic properties and temperature-dependent leakage mechanism of Sc-substituted bismuth ferritendashlead titanatethin filmsF Yan et al

-

Magnetoelectric behavior of ferrimagneticBixCo2xMnO4 (x=0 01 and 03) thin filmsNE Rajeevan et al

-

This content was downloaded from IP address 12237911 on 23092021 at 0546

Pulsed laser deposition and characterization of (BiFeO3)07-(PbTiO3)03 thin films

M A Khan A Garg and A J Bell

Institute for Materials Research University of Leeds LS2 9JT

Abstract Development of ferroelectric materials and their composites has been a subject of intensive investigation in recent years due to their promise in next generation electronic devices In this work we report on the pulsed laser deposition of thin films of bismuth ferrite lead titanate (BiFeO3)x-(PbTiO3)1-x on platinized Si (100) substrates The growth conditions were optimised by changing a range of growth parameters such as background pressure growth temperature and laser frequency The film structure was studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) We found that films become highly Pb and Bi deficient upon increasing the deposition temperatures up to 600degC A stoichiometric BFPT 7030 phase was observed at a substrate temperature of 450ordmC In addition it was observed that the phase orientation of films prepared at a substrate temperature of 450ordmC can be enhanced by post deposition annealing resulting in a dense columnar grain growth of the film

1 Introduction Interest in the development of ferroelectric materials in the form of thin films is due to their potential for use in next generation electronic and memory devices eg ferroelectric random access memories (FeRAMs) piezoelectric actuators and micro electromechanical systems (MEMS) This research interest has been further fuelled by the possibility of developing multiferroic materials for memory device applications such as spintronic and data storage devices The latter are special types of ferroelectrics which exhibit ferromagnetism as well and thus an entire new range of applications based on coupling to either of their ferroelectric or ferromagnetic polarizations can be envisaged eg multiple state memory elements in which data can be stored in both the electric and magnetic polarizations [1]

BFPT (BiFeO3)x-(PbTiO3)1-x is a solid solution of bismuth ferrite and lead titanate Ferroelectric bismuth ferrite BiFeO

3 exhibits a rhombohedral distorted perovskite structure below 850ordmC while

PbTiO3 has a tetragonally distorted perovskite structure below 490ordmC [2] There is a morphotropic phase boundary (MPB) separating the tetragonal and rhombohedral phase around x = 07 similar to that in PZT (lead zirconate titanate) [3] The ca ratio on the tetragonal side of the MPB has been reported to be as high as 1187 [4] compared to that of an end member value of 106 for PbTiO

3 [5]

The existence of paramagnetic Fe3+ ions in this solid solution also suggests that the material should exhibit ferromagnetic properties [6] Thus the presence of a high ferroelectric strain combined with the presence of weak ferromagnetism [6] signify the potential of this material for thin film device applications

For thin film preparation various deposition methods in case of a similar compound ie PZT have been based on ion beam sputtering [7] rf planar magnetron sputtering [8] sol-gel [9] metal organic chemical vapour deposition (MOCVD) [8] and more recently pulsed laser deposition (PLD) [101112] In the present work the preparation of thin films of BFPT has been carried out using

Institute of Physics Publishing Journal of Physics Conference Series 26 (2006) 288ndash291doi1010881742-6596261069 EMAGndashNANO 05 Imaging Analysis and Fabrication on the Nanoscale

288copy 2006 IOP Publishing Ltd

pulsed laser deposition This is a fast developing technique allowing highly controlled in-situ growth of thin films in an efficient and effective manner It is applicable in particular to complex compounds that are difficult to produce in thin-film form by other techniques [12]

2 Experimental BFPT powders with a composition near the morphotropic phase boundary (BiFeO3)07(PbTiO3)03 were prepared from powders of PbO (gt99 purity Aldrich Germany) TiO2 (gt99 purity Aldrich Germany) Bi

2O

3 (gt99 purity Aldrich Germany) and Fe

2O

3 (gt99 purity Aldrich Germany) The

powders were attrition milled (Type KDLA Bachofen AG Basel Switzerland) for 30 minutes with stabilized zirconia balls in iso-propyl alcohol (IPA) followed by drying and sieving The powders were calcined at 800 ordmC for 2 hours to induce the required chemical reaction This was followed by isostatic pressing of targets at 400 MPa and subsequent sintering at 1000 ordmC

Pulsed laser deposition (PLD) was performed using a Surface PLD Workstation (Surface Huumlckelhoven Germany) incorporating a Tui Thin Film Star 248 nm KrF laser system (Tui Laser AG Munich Germany) A laser beam operating at 5 Hz was directed in a chamber with 150 mTorr of oxygen pressure and focused on the BFPT target The incident laser fluence was set at 6 Jcm2 The interaction of the laser beam with the target results in the formation of a highly directed plasma plume The plasma plume transfers the ablated material from the target surface to the heated substrate held at a distance of 4cm from the target Films were deposited at substrate temperatures varying from 450 ordmC to 650ordmC Films prepared at 450 ordmC were also subjected a 1 hr post deposition anneal at 350 ordmC

PtSi wafers (100) were used as substrates which were chosen to facilitate the integration of such films with current semi-conductor technologies The wafers were composed of a silicon base layer with a SiO

2 thermal oxide layer a 5 nm Ti layer and a 100 nm Pt layer The substrates were

ultrasonically cleaned in volasil acetone and iso-propanol respectively This was followed by a rinse in de-ionized water and blow drying

The characterisation of the film properties was performed using x-ray diffraction (Model Xrsquopert PRO MPD PANalytical Almelo The Netherlands) optical microscopy SEM and EDX (Model 1530 FEGSEM LEO electron microscopy group Oberkochen Germany) analysis to ascertain the phase surface morphology and chemical composition respectively The SEM images were obtained using a secondary electron in lens detector

3 Results and Discussion Diffraction patterns for the films prepared at varying substrate deposition temperatures are shown in Figure 1 It was observed that at temperatures above 500 ordmC BFPT perovskite phase formation was not observed This was thought to be due to the loss of bismuth and lead contents from the film surface at the elevated substrate temperature due to their intrinsic volatile nature EDX analysis performed on film surfaces confirmed this indicating a substantial loss in the bismuth content above 500 ordmC with lead loss becoming appreciable above 550 ordmC while films formed at 450 ordmC maintained target stoichiometry An oriented phase development of BFPT 7030 was observed at a substrate deposition temperature of 450 ordmC These films were further subjected to an annealing treatment for one hour at 350 ordmC and the resulting diffraction patterns are shown in Figure 2 It was observed that the post deposition annealing results in further enhancing the degree of orientation within the film with the film exhibiting improved (001) orientation of a tetragonal BFPT 7030 phase In addition the presence of weak rhombohedral 110 peaks suggest the presence of a mixed phase

The surface morphology of the films prepared at 600 ordmC and 450 ordmC before annealing was examined by scanning electron microscopy (Figure 3 and Figure 4 respectively) It can be seen that while films deposited at a substrate temperature of 600 ordmC have a fair degree of porosity with a grain size ranging from 45 nm to 230 nm (mean ~115 nm) those deposited at 450 ordmC are dense and exhibit an oriented layer on layer grain growth mode resulting in the observed terrace formations The latter exhibiting a grain size range from 65 nm to 230 nm (mean ~ 120 nm)

289

Figure 3 SEM of film deposited at a substrate temperature of 600ordmC before annealing

300 nm

Figure 4 SEM of film deposited at a substrate temperature of 450ordmC before annealing

300 nm

Figure 5 SEM of film deposited at a substrate temperature of 450ordmC after annealing

300 nm

SiO2

Silicon

Pt

BFPT

Figure 6 SEM of film cross section deposited at a substrate temperature of 450ordmC after annealing

300 nm

Figure 1 X-ray diffraction pattern of BFPT 7030 films at varying substrate temperatures

10 20 30 40 50 60 70degrees 2-theta

600ordmC

550ordmC

500ordmC

450ordmC

PbOFe2O3

TiO2

Pt(1

11)

Si(4

00)

Si(2

00)

(001

) T(0

01) T

(100

) T(1

00) R

(200

) R(2

00) T

(101

) T(1

01) T

(110

) T(1

10) T

(110

) R(1

10) R

Figure 2 X-ray diffraction pattern of BFPT 7030 deposited at a substrate temperature of 450ordmC before and after annealing

10 20 30 40 50 60 70degrees 2-theta

After annealing

Before annealing

Pt(1

11)

Si(4

00)

(001

) T

(003

) T

Si(2

00)

(110

) R(1

01) T

(110

) R(101

) T

(100

) R(001

) T

Si(2

00)

(110

) T(1

10) T

(100

) T

290

Figure 5 is a SEM image of an annealed film We can observe two types of grain morphologies one exhibiting terraced grain growth which is parallel to the film surface and appear as flat grains while other grains appear to be growing at angles not parallel to the film surface and exhibit a prism like morphology in which three faces of the grains are visible with its corner pointing out of plane This growth mode could be a result of lattice strain being induced due to a lattice mismatch between the platinum substrate and the BFPT film thus constraining uniform growth of the film parallel to the substrate and possibly leading to the twin orientation of the film This is under further investigation under TEM

Cross-sectional SEM of the film revealed highly oriented dense columnar grain growth as shown in Figure 6 This growth mode was expected as the XRD patterns had indicated a predominantly oriented crystal orientation along the (00l) ie c-axis The surface morphology also shows grains formed with triangular tips with the apex angle close to 120ordm ranging between 110ordm and 120ordm which is reminiscent of a threefold growth symmetry

4 Conclusion

Development of a stoichiometric BFPT 7030 phase in thin films using pulsed laser deposition was observed at a substrate temperature of 450ordmC The lack of phase formation at higher substrate temperatures was attributed to the loss of volatile constituents of bismuth and lead The phase orientation of films prepared at a substrate temperature of 450ordmC can be enhanced by post deposition annealing resulting in a dense columnar grain growth of the film

Acknowledgements We would like to thank Prof Rik Brydson Dr Tim Comyn and Dr Andy Brown for their enthusiastic support and input

References [1] Hill N A 2000 J Phys Chem B 104 (29) 6694-6709 [2] Khan M A Comyn T P and Bell A J 2005 J Am Ceram Soc In print [3] Jaffe B Cook W R and Jaffe H 1971 Piezoelectric ceramics Academic London [4] Sunder S Halliyal A and Umarji A M 1995 J Mater Res 10 1301-1306 [5] Woodward D I Reaney I M 2003 J Appl Phys 94 (5) 3313-3318 [6] Fedulov S A Ladyzhinskii P B Pyatigoskaya I L and Venevtsev Yu N 1964 Sov Phys-Sol

State [7] Castellano R and Feinstein L G 1979 J Appl Phys 50 4406-4411 [8] Krupanidhi S B Maffei N Sayer M Assal K El 1983 J Appl Phys 54 6601-6609 [9] Muralt P 2000 IEEE Trans Ultrasonics Ferroelectrics and Frequency Control 47 (4) 903-915 [10] Chrisey D B and Hubler G K 1994 Pulsed laser deposition of thin films Wiley New York [11] Paz de Araujo C Scott J F and Taylor G W 1996 Ferroelectric thin films synthesis and basic

properties Gordon and Breach Amsterdam [12] Ohring M 2002 Materials science of thin films deposition and structure Academic press San

Diego

291

pulsed laser deposition This is a fast developing technique allowing highly controlled in-situ growth of thin films in an efficient and effective manner It is applicable in particular to complex compounds that are difficult to produce in thin-film form by other techniques [12]

2 Experimental BFPT powders with a composition near the morphotropic phase boundary (BiFeO3)07(PbTiO3)03 were prepared from powders of PbO (gt99 purity Aldrich Germany) TiO2 (gt99 purity Aldrich Germany) Bi

2O

3 (gt99 purity Aldrich Germany) and Fe

2O

3 (gt99 purity Aldrich Germany) The

powders were attrition milled (Type KDLA Bachofen AG Basel Switzerland) for 30 minutes with stabilized zirconia balls in iso-propyl alcohol (IPA) followed by drying and sieving The powders were calcined at 800 ordmC for 2 hours to induce the required chemical reaction This was followed by isostatic pressing of targets at 400 MPa and subsequent sintering at 1000 ordmC

Pulsed laser deposition (PLD) was performed using a Surface PLD Workstation (Surface Huumlckelhoven Germany) incorporating a Tui Thin Film Star 248 nm KrF laser system (Tui Laser AG Munich Germany) A laser beam operating at 5 Hz was directed in a chamber with 150 mTorr of oxygen pressure and focused on the BFPT target The incident laser fluence was set at 6 Jcm2 The interaction of the laser beam with the target results in the formation of a highly directed plasma plume The plasma plume transfers the ablated material from the target surface to the heated substrate held at a distance of 4cm from the target Films were deposited at substrate temperatures varying from 450 ordmC to 650ordmC Films prepared at 450 ordmC were also subjected a 1 hr post deposition anneal at 350 ordmC

PtSi wafers (100) were used as substrates which were chosen to facilitate the integration of such films with current semi-conductor technologies The wafers were composed of a silicon base layer with a SiO

2 thermal oxide layer a 5 nm Ti layer and a 100 nm Pt layer The substrates were

ultrasonically cleaned in volasil acetone and iso-propanol respectively This was followed by a rinse in de-ionized water and blow drying

The characterisation of the film properties was performed using x-ray diffraction (Model Xrsquopert PRO MPD PANalytical Almelo The Netherlands) optical microscopy SEM and EDX (Model 1530 FEGSEM LEO electron microscopy group Oberkochen Germany) analysis to ascertain the phase surface morphology and chemical composition respectively The SEM images were obtained using a secondary electron in lens detector

3 Results and Discussion Diffraction patterns for the films prepared at varying substrate deposition temperatures are shown in Figure 1 It was observed that at temperatures above 500 ordmC BFPT perovskite phase formation was not observed This was thought to be due to the loss of bismuth and lead contents from the film surface at the elevated substrate temperature due to their intrinsic volatile nature EDX analysis performed on film surfaces confirmed this indicating a substantial loss in the bismuth content above 500 ordmC with lead loss becoming appreciable above 550 ordmC while films formed at 450 ordmC maintained target stoichiometry An oriented phase development of BFPT 7030 was observed at a substrate deposition temperature of 450 ordmC These films were further subjected to an annealing treatment for one hour at 350 ordmC and the resulting diffraction patterns are shown in Figure 2 It was observed that the post deposition annealing results in further enhancing the degree of orientation within the film with the film exhibiting improved (001) orientation of a tetragonal BFPT 7030 phase In addition the presence of weak rhombohedral 110 peaks suggest the presence of a mixed phase

The surface morphology of the films prepared at 600 ordmC and 450 ordmC before annealing was examined by scanning electron microscopy (Figure 3 and Figure 4 respectively) It can be seen that while films deposited at a substrate temperature of 600 ordmC have a fair degree of porosity with a grain size ranging from 45 nm to 230 nm (mean ~115 nm) those deposited at 450 ordmC are dense and exhibit an oriented layer on layer grain growth mode resulting in the observed terrace formations The latter exhibiting a grain size range from 65 nm to 230 nm (mean ~ 120 nm)

289

Figure 3 SEM of film deposited at a substrate temperature of 600ordmC before annealing

300 nm

Figure 4 SEM of film deposited at a substrate temperature of 450ordmC before annealing

300 nm

Figure 5 SEM of film deposited at a substrate temperature of 450ordmC after annealing

300 nm

SiO2

Silicon

Pt

BFPT

Figure 6 SEM of film cross section deposited at a substrate temperature of 450ordmC after annealing

300 nm

Figure 1 X-ray diffraction pattern of BFPT 7030 films at varying substrate temperatures

10 20 30 40 50 60 70degrees 2-theta

600ordmC

550ordmC

500ordmC

450ordmC

PbOFe2O3

TiO2

Pt(1

11)

Si(4

00)

Si(2

00)

(001

) T(0

01) T

(100

) T(1

00) R

(200

) R(2

00) T

(101

) T(1

01) T

(110

) T(1

10) T

(110

) R(1

10) R

Figure 2 X-ray diffraction pattern of BFPT 7030 deposited at a substrate temperature of 450ordmC before and after annealing

10 20 30 40 50 60 70degrees 2-theta

After annealing

Before annealing

Pt(1

11)

Si(4

00)

(001

) T

(003

) T

Si(2

00)

(110

) R(1

01) T

(110

) R(101

) T

(100

) R(001

) T

Si(2

00)

(110

) T(1

10) T

(100

) T

290

Figure 5 is a SEM image of an annealed film We can observe two types of grain morphologies one exhibiting terraced grain growth which is parallel to the film surface and appear as flat grains while other grains appear to be growing at angles not parallel to the film surface and exhibit a prism like morphology in which three faces of the grains are visible with its corner pointing out of plane This growth mode could be a result of lattice strain being induced due to a lattice mismatch between the platinum substrate and the BFPT film thus constraining uniform growth of the film parallel to the substrate and possibly leading to the twin orientation of the film This is under further investigation under TEM

Cross-sectional SEM of the film revealed highly oriented dense columnar grain growth as shown in Figure 6 This growth mode was expected as the XRD patterns had indicated a predominantly oriented crystal orientation along the (00l) ie c-axis The surface morphology also shows grains formed with triangular tips with the apex angle close to 120ordm ranging between 110ordm and 120ordm which is reminiscent of a threefold growth symmetry

4 Conclusion

Development of a stoichiometric BFPT 7030 phase in thin films using pulsed laser deposition was observed at a substrate temperature of 450ordmC The lack of phase formation at higher substrate temperatures was attributed to the loss of volatile constituents of bismuth and lead The phase orientation of films prepared at a substrate temperature of 450ordmC can be enhanced by post deposition annealing resulting in a dense columnar grain growth of the film

Acknowledgements We would like to thank Prof Rik Brydson Dr Tim Comyn and Dr Andy Brown for their enthusiastic support and input

References [1] Hill N A 2000 J Phys Chem B 104 (29) 6694-6709 [2] Khan M A Comyn T P and Bell A J 2005 J Am Ceram Soc In print [3] Jaffe B Cook W R and Jaffe H 1971 Piezoelectric ceramics Academic London [4] Sunder S Halliyal A and Umarji A M 1995 J Mater Res 10 1301-1306 [5] Woodward D I Reaney I M 2003 J Appl Phys 94 (5) 3313-3318 [6] Fedulov S A Ladyzhinskii P B Pyatigoskaya I L and Venevtsev Yu N 1964 Sov Phys-Sol

State [7] Castellano R and Feinstein L G 1979 J Appl Phys 50 4406-4411 [8] Krupanidhi S B Maffei N Sayer M Assal K El 1983 J Appl Phys 54 6601-6609 [9] Muralt P 2000 IEEE Trans Ultrasonics Ferroelectrics and Frequency Control 47 (4) 903-915 [10] Chrisey D B and Hubler G K 1994 Pulsed laser deposition of thin films Wiley New York [11] Paz de Araujo C Scott J F and Taylor G W 1996 Ferroelectric thin films synthesis and basic

properties Gordon and Breach Amsterdam [12] Ohring M 2002 Materials science of thin films deposition and structure Academic press San

Diego

291

Figure 3 SEM of film deposited at a substrate temperature of 600ordmC before annealing

300 nm

Figure 4 SEM of film deposited at a substrate temperature of 450ordmC before annealing

300 nm

Figure 5 SEM of film deposited at a substrate temperature of 450ordmC after annealing

300 nm

SiO2

Silicon

Pt

BFPT

Figure 6 SEM of film cross section deposited at a substrate temperature of 450ordmC after annealing

300 nm

Figure 1 X-ray diffraction pattern of BFPT 7030 films at varying substrate temperatures

10 20 30 40 50 60 70degrees 2-theta

600ordmC

550ordmC

500ordmC

450ordmC

PbOFe2O3

TiO2

Pt(1

11)

Si(4

00)

Si(2

00)

(001

) T(0

01) T

(100

) T(1

00) R

(200

) R(2

00) T

(101

) T(1

01) T

(110

) T(1

10) T

(110

) R(1

10) R

Figure 2 X-ray diffraction pattern of BFPT 7030 deposited at a substrate temperature of 450ordmC before and after annealing

10 20 30 40 50 60 70degrees 2-theta

After annealing

Before annealing

Pt(1

11)

Si(4

00)

(001

) T

(003

) T

Si(2

00)

(110

) R(1

01) T

(110

) R(101

) T

(100

) R(001

) T

Si(2

00)

(110

) T(1

10) T

(100

) T

290

Figure 5 is a SEM image of an annealed film We can observe two types of grain morphologies one exhibiting terraced grain growth which is parallel to the film surface and appear as flat grains while other grains appear to be growing at angles not parallel to the film surface and exhibit a prism like morphology in which three faces of the grains are visible with its corner pointing out of plane This growth mode could be a result of lattice strain being induced due to a lattice mismatch between the platinum substrate and the BFPT film thus constraining uniform growth of the film parallel to the substrate and possibly leading to the twin orientation of the film This is under further investigation under TEM

Cross-sectional SEM of the film revealed highly oriented dense columnar grain growth as shown in Figure 6 This growth mode was expected as the XRD patterns had indicated a predominantly oriented crystal orientation along the (00l) ie c-axis The surface morphology also shows grains formed with triangular tips with the apex angle close to 120ordm ranging between 110ordm and 120ordm which is reminiscent of a threefold growth symmetry

4 Conclusion

Development of a stoichiometric BFPT 7030 phase in thin films using pulsed laser deposition was observed at a substrate temperature of 450ordmC The lack of phase formation at higher substrate temperatures was attributed to the loss of volatile constituents of bismuth and lead The phase orientation of films prepared at a substrate temperature of 450ordmC can be enhanced by post deposition annealing resulting in a dense columnar grain growth of the film

Acknowledgements We would like to thank Prof Rik Brydson Dr Tim Comyn and Dr Andy Brown for their enthusiastic support and input

References [1] Hill N A 2000 J Phys Chem B 104 (29) 6694-6709 [2] Khan M A Comyn T P and Bell A J 2005 J Am Ceram Soc In print [3] Jaffe B Cook W R and Jaffe H 1971 Piezoelectric ceramics Academic London [4] Sunder S Halliyal A and Umarji A M 1995 J Mater Res 10 1301-1306 [5] Woodward D I Reaney I M 2003 J Appl Phys 94 (5) 3313-3318 [6] Fedulov S A Ladyzhinskii P B Pyatigoskaya I L and Venevtsev Yu N 1964 Sov Phys-Sol

State [7] Castellano R and Feinstein L G 1979 J Appl Phys 50 4406-4411 [8] Krupanidhi S B Maffei N Sayer M Assal K El 1983 J Appl Phys 54 6601-6609 [9] Muralt P 2000 IEEE Trans Ultrasonics Ferroelectrics and Frequency Control 47 (4) 903-915 [10] Chrisey D B and Hubler G K 1994 Pulsed laser deposition of thin films Wiley New York [11] Paz de Araujo C Scott J F and Taylor G W 1996 Ferroelectric thin films synthesis and basic

properties Gordon and Breach Amsterdam [12] Ohring M 2002 Materials science of thin films deposition and structure Academic press San

Diego

291

Figure 5 is a SEM image of an annealed film We can observe two types of grain morphologies one exhibiting terraced grain growth which is parallel to the film surface and appear as flat grains while other grains appear to be growing at angles not parallel to the film surface and exhibit a prism like morphology in which three faces of the grains are visible with its corner pointing out of plane This growth mode could be a result of lattice strain being induced due to a lattice mismatch between the platinum substrate and the BFPT film thus constraining uniform growth of the film parallel to the substrate and possibly leading to the twin orientation of the film This is under further investigation under TEM

Cross-sectional SEM of the film revealed highly oriented dense columnar grain growth as shown in Figure 6 This growth mode was expected as the XRD patterns had indicated a predominantly oriented crystal orientation along the (00l) ie c-axis The surface morphology also shows grains formed with triangular tips with the apex angle close to 120ordm ranging between 110ordm and 120ordm which is reminiscent of a threefold growth symmetry

4 Conclusion

Development of a stoichiometric BFPT 7030 phase in thin films using pulsed laser deposition was observed at a substrate temperature of 450ordmC The lack of phase formation at higher substrate temperatures was attributed to the loss of volatile constituents of bismuth and lead The phase orientation of films prepared at a substrate temperature of 450ordmC can be enhanced by post deposition annealing resulting in a dense columnar grain growth of the film

Acknowledgements We would like to thank Prof Rik Brydson Dr Tim Comyn and Dr Andy Brown for their enthusiastic support and input

References [1] Hill N A 2000 J Phys Chem B 104 (29) 6694-6709 [2] Khan M A Comyn T P and Bell A J 2005 J Am Ceram Soc In print [3] Jaffe B Cook W R and Jaffe H 1971 Piezoelectric ceramics Academic London [4] Sunder S Halliyal A and Umarji A M 1995 J Mater Res 10 1301-1306 [5] Woodward D I Reaney I M 2003 J Appl Phys 94 (5) 3313-3318 [6] Fedulov S A Ladyzhinskii P B Pyatigoskaya I L and Venevtsev Yu N 1964 Sov Phys-Sol

State [7] Castellano R and Feinstein L G 1979 J Appl Phys 50 4406-4411 [8] Krupanidhi S B Maffei N Sayer M Assal K El 1983 J Appl Phys 54 6601-6609 [9] Muralt P 2000 IEEE Trans Ultrasonics Ferroelectrics and Frequency Control 47 (4) 903-915 [10] Chrisey D B and Hubler G K 1994 Pulsed laser deposition of thin films Wiley New York [11] Paz de Araujo C Scott J F and Taylor G W 1996 Ferroelectric thin films synthesis and basic

properties Gordon and Breach Amsterdam [12] Ohring M 2002 Materials science of thin films deposition and structure Academic press San

Diego

291