The paper analyzes the process of formation and subsequent deposition of monolayers stabilized in sodium
oleate nanoparticles of barium titanate. X-ray diffractometer studies conducted particle size distribution
of the ferroelectric particles deposited. Probe technique was used to study the effect of matter and the
wettability of the underlayer on the structure and quality of deposited coatings. The possibility of recording
ferroelectric domains produced thin Langmuir films of barium titanate

Abakumov, P.V.

Chuhaeva, I.V.

Dobromyslov, M.B.

Emelyanov, N.A.

Kuzmenko, A.P.

English

SocioEconomic Challenges Journal (Sumy State University)

ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ JOURNAL OF NANO- AND ELECTRONIC PHYSICS  
Том 7 № 4, 04025(4cc) (2015) Vol. 7 No 4, 04025(4pp) (2015) 
 
 
2077-6772/2015/7(4)04025(4) 04025-1  2015 Sumy State University 
An Analysis of the Deposition Process and the Structure of Ferroelectric Langmuir Films of 
Barium Titanate 
 
A.P. Kuzmenko1,*, I.V. Chuhaeva1, P.V. Abakumov1, M.B. Dobromyslov2, N.A. Emelyanov3 
 
1 South-West State University, 94, 50 let Octyabrya St., 305040 Kursk, Russia 
2 Pacific National University, 136, Tihookeanskaya St., 680035 Khabarovsk, Russia 
3 Kursk State University, 33, Radisheva St., 305000 Kursk, Russia 
 
(Received 23 September 2015; published online 10 December 2015) 
 
The paper analyzes the process of formation and subsequent deposition of monolayers stabilized in so-
dium oleate nanoparticles of barium titanate. X-ray diffractometer studies conducted particle size distribu-
tion of the ferroelectric particles deposited. Probe technique was used to study the effect of matter and the 
wettability of the underlayer on the structure and quality of deposited coatings. The possibility of recording 
ferroelectric domains produced thin Langmuir films of barium titanate. 
 
Keywords:: Langmuir-Blodgett films, Scanning microscopy, Scanning probe microscopy, Surface poten-
tial, -А isotherms, Ferroelectric. 
 
 PACS numbers: 68.18. – g, 68.47.Pe, 68.37.Ps, 
85.50. – n 
 
 
                                                          
* apk3527@mail.ru 
Synthesis of monolayered materials of organic, non-
organic, and mixed nature is of great interest, which is 
due to the necessity of obtaining unique set of features 
needed in various fields of science and engineering [1]. 
A lot of methods for producing such materials exist 
(direct synthesis, crystallization, self-organization, etc.) 
but the Langmuir-Blodgett method (LB) is of most 
interest at present. The method makes it possible to 
produce thin films of a set thickness without special 
conditions: vacuum, high temperatures and pressures, 
degassing. Fat acids and their salts are the typical 
materials for Langmuir films. These are amphiphilic to 
produce stabilized monolayers. For a number of chal-
lenges, it is necessary to obtain thin films from materi-
als not diphilic but having needed features. One of 
those materials is barium titanate, BaTiO3, (BTO). 
BTO is ferroelectric with photorefractive and piezoelec-
tric effects, featuring super high permittivity, high 
Curie temperature (120 С), thermo- and mechanical 
resistance, and also electrooptic and dielectric proper-
ties [2]. Unique properties of BTO are used in capaci-
tors, optoelectronic devices, piezoelectric transducers, 
and MEMS devices [3]. 
The present paper has determined optimum deposi-
tion parameters of stabilized BTO particles with LB 
method. Also, temperature dependencies of -А iso-
therms, the hysteresis of compression-extension pro-
cesses and changes in the surface potential are ana-
lyzed. The influence of substrates on the quality of 
deposited BTO films and polarizability of a thin barium 
titanate film according to electrostatic force microscopy 
are studied. 
To produce Langmuir monolayers, BTO nanoparti-
cles of an almost spherical shape obtained by peroxide 
synthesis in tetragonal and cube phase were used [4]. 
Stabilization of nanoparticles was achieved by satura-
tion of their surfaces with hydroxyl groups OH with 
boiling in 30 % hydrogen peroxide solution for three 
hours. Hydroxylated nanoparticles obtained were also 
modified with sodium oleate C17H33COONa molecules 
by vigorous agitation in 0.5 % water solution at 85 °C 
for four hours as in [5, 6]. Homogeneity of colloidal BTO 
solutions was enhanced at centrifuge MiniSpin plus, 
Eppendorf. 
Investigations were conducted with plant KSV NI-
MA 2002 [7] that featured built-in thermostat JULABO 
F12-ED ((– 20 +100) ± 0.03 °C) and device (SPOT) for 
surface potential measurement (300 Hz, 1 mV). The 
formation was visualized with Brewster microscope 
MicroBAM (resolution 12 m). -А isotherms (error 
5 N/m) and surface potential were obtained with dis-
cretization period of slightly more than 1 s, and the 
total number of points was several thousands. Mor-
phology of BTO monolayers was examined with atomic-
force microscope (AFM) AIST-NT in a semi contact 
mode (cantilever with standard silicon probe). Particle 
size distribution DV(r) was plotted based on data of 
small-angle X-ray scattering (SAXS) that were obtained 
at plant SAXSess mc2 (Anton Paar, Austria) in a linear 
collimation mode (Cu Kα with a wavelength of 
0.154 nm within range from 0.03 to 28 nm – 1 with a 
resolution of 0.03 nm – 1). Ferroectric properties of mon-
olayers were studied at SPM NTegra Aura (NT-MDT) 
with platinum coating conductive probe.  
Particle size distribution DV(r) according to SAXS is 
given in Fig. 1. As is seen, averaged radii of synthe-
sized particles were 5, 12, and 27 nm. 
For optimization of deposition parameters of BTO 
А isotherms were constructed at various BTO vol-
umes, barrier velocities, and temperatures. Thus, the 
rational parameters of deposition are the following: 
volume – 3 l, the barrier velocity – 5 mm/min, pres-
sure of transfer – 25 mN/m, temperature – 295 K. 
Analysis of images in microscope MicroBAM [8] re-
veals that (Fig.2) monolayer begins its formation even 
at   0.16 mN/m. In doing so, drop-like structures 
start to form the size of up to 120 m that are divided 
by small water areas. Beginning with   9 µm, they are 
 A.P. KUZMENKO, I.V. CHUHAEVA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04025 (2015) 
 
 
04025-2 
 
 
Fig. 1 – Granulometric analysis of BTO nanoparticles 
 
 
 
Fig. 2 – Data of angle Brewster microscopy at compression-
extension of BTO monolayer 
 
joined to produce ellipsoid-like structures with axes of 
the order of 200 and 400 m. At a pressure of 25 mN/m, 
a compact monolayer is formed. The further pressure 
increase did not produce collapse, which is probably 
due to the transfer of particles from the water surface 
into internal layers of the subphase. This is supported 
by the film destruction at its extension starting with 
  2.5 mN/m. 
As is seen from images of MicroBAM, at tempera-
tures of 283 and 310 K the formation of nonzero thick-
ness domains occurs only to the surface pressure of 
  0.3 mN/m (Fig. 3). With further increase in pressure 
at such temperatures monolayers do not form. At the 
start of film formation at a temperature of 295 K, the 
domain area is not large and the domains are located 
far away from each other. At this temperature with 
pressure increasing domains are joined to produce a 
uniform monolayer. According to the classification [9], 
the nature of isotherms corresponds to the “gas-solid” 
phase transition. Brewster images of monolayers 
(Fig. 3) at T  283, 310, and 295 K are noticeably dif-
ferent, which is indicative of an essential temperature 
effect on phase transitions at BTO monolayer for-
mation. 
Measurement of -A isotherms and the surface po-
tential given in Fig. 4 were conducted during two con-
traction-extension cycles of a monolayer under study.  
 
 
Fig. 3 – Microscopy under Brewster angle of BTO monolayers 
at various temperatures (  0.3 mN/m) 
 
With every cycle, an increase in area per molecule was 
noted (at contraction from 290 Å2 to 380 Å2, at an ex-
tension from 240 Å2 to 300 Å2 at a pressure of 
25 mN/m). This may be explained by the domain for-
mation, which impedes the successive film decay into 
individual particles at its extension. The inferences 
obtained from analysis of united -A dependencies and 
surface potential that provide a qualitative picture 
about phase transitions and the processes of both for-
mation and destruction of the monolayer are in accord 
with inferences [10]. 
At contraction, a sharp increase in surface potential is 
observed, which corresponds to the onset of film formation 
and is corroborated by Brewster microscopy. Relative to 
the point of surface potential increase, the area per mole-
cule before the film formation in the first cycle is 454 Å2, 
whereas at the second cycle – 474 Å2 (Fig. 4). 
 
 
 
Fig. 4 – Hysteresis of contraction-extension (1) and surface 
potential (2) for BTO 
 
The surface potential for the second cycle is reduced 
by 0.08 V. At greater number of cycles, the similar 
dependence occurs, that is surface potential of the 
monolayer is reciprocally proportional to the area per 
molecule in accord to the inferences [11]: 
 
 ΔU  /(ε0ε1A) (1) 
 AN ANALYSIS OF THE DEPOSITION PROCESS… J. NANO- ELECTRON. PHYS. 7, 04025 (2015) 
 
 
04025-3 
where  is a vertical component of the dipole momen-
tum, ɛ0 is the dielectric constant, ɛ1 is permittivity of 
the monolayer, А is the area per molecule. Of note is 
the fact that according to (1), from measured U and A, 
with consideration for values of 1 a vertical component 
of the dipole momentum  may be determined. 
With consideration for [12], the role of both quality 
of substrate surface and their structure in the LB for-
mation of BTO monolayers was considered. To this end, 
the substrates of amorphous (glass), single crystal (sili-
con KDB (100)) and poly crystal at a glass from magne-
tron films Pt and Ni with Cr were prepared. Deposition 
of monolayered LB films from stabilized BTO was con-
ducted by the vertical lift with consideration for the 
noted parameters of deposition by transfer of distilled 
water from the surface to the substrates. The total 
number of philic substrates was 7, for hydrophobic 
substrates – 8. The values of BTO transfer coefficients 
to the substrates under study, which were determined 
by the difference S – S – areas before and after trans-
fer of ВТО to the substrate with respect to the sub-
strate area – S: 
 
 k  (S – S) / S  
 
turned out to be different. Their values are given in 
Table 1. The closest to unity transfer coefficient was for 
Pt substrate, which may be indicative of uniformity of 
the BTO monolayer formed. 
 
Table 1 – Transfer coefficients of LB films of BTO to various 
substrates 
 
Substrate Glass Si Pt Ni 
Transfer 
coefficient 
0.6-1.19 0.4-1.1 0.9-1.2 0.1-0.3 
 
AFM-images of surfaces and one of profilograms for 
the substrates under study and formed on them BTO 
monolayers are shown in Fig. 5. As is well known, 
magnetron coatings are characterized in the deposition 
process by the formation of cluster structures, which is 
supported by Fig. 5, I and II). The comparison of imag-
es before (Fig. 5, I and II) and after deposition of BTO 
(Fig. 5, I and II) shows that for Pt the initial cluster 
structure was fully covered with nearly-the-same size 
nanoparticles as regular rows. At the same time, for Ni, 
clusters are evidently observed. It should be noted that 
the AFM-images of the original surfaces of glass and 
silicon are without clusters. After BTO deposition, 
nanoparticles do not become more ordered, which is 
seen from the comparison of images before (Fig. 5, III 
and IV) and after BTO deposition (Fig. 5, III и IV). 
 
      
 
       
 
        
 
       
 
Fig. 5 – AFM-images of topology of substrate surfaces from Pt – 
I, Ni – II, glass – III and silicon – IV and BTO monolayers (ver-
tical deposition) onto magnetron films Pt – I and Ni – II, and 
substrates from glass – III and silicon – IV 
 
The results of the granulometric analysis of BTO 
monolayer surfaces are given in Table 2. Average size 
of BTO particles coincide at deposition onto Pt and Si 
substrates (Fig.5, I and IV), which correlates with the 
transfer coefficient value (Table 1) and is supported by 
the surface profiles where changes in height turned out 
to be equal and were 7 nm. For a film at the substrate 
with magnetron film nickel with transfer coefficient 
significantly smaller than unity (Table 1) AFM-image 
(Fig. 5, II) demonstrates that BTO particles  virtually 
coincide in size with size of the film structures at the 
substrate itself. 
 
Table 2 – Topological size of substrate surface before and 
after BTO deposition 
 
Substrate type  Average particle size, nm  
Substrate  Film  
Platinum / glass  10 7 
Nickel / Glass  5 6 
Glass 4 4 
Silicon  2 7 
 
Reasonably high value of k  0.6–1.19 might be ex-
pected to cause the film formation onto the glass. How-
ever, average size characterized both the glass surface 
itself and possible deposition of BTO particles onto it 
turns out to be equal. 
To determine the fact of BTO deposition onto glass 
as well as other substrates, with an optical microscope 
by drop projection wetting angles θ were measured that 
are given in Table 3. It proved to be that Pt and Si 
 A.P. KUZMENKO, I.V. CHUHAEVA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04025 (2015) 
 
 
04025-4 
substrates had the least values of θ whereas its value 
for Ni and glass increased several times although did 
not reach  / 2. This fact may be indicative either of 
pure quality of a formed film or, in general, its absence 
at all. This conclusion is in accord with data from Ta-
ble 2 where just on these substrates the average char-
acteristic size after BTO deposition for glass did not 
change, and for Ni differed slightly – 1 nm (accuracy of 
measurement was 20 pm). 
 
Table 3 – The wetting angle of colloidal solution of BTO onto 
substrates under study 
 
Substrate for BTO  
deposition 
Glass Ni  Si Pt 
Wetting angle,  (deg.) 67 55 35 10 
 
The results on BTO deposition at various substrates 
under equal conditions, as is shown in Table 1-3 and 
Fig. 5, are indicative of the fact that the LB films of 
BTO are of higher quality at Platinum substrate. 
Thus, to study the ferroelectric properties of the 
films was selected substrate with a platinum sublayer. 
Using microscopy piezoelectric response the film 
surface with an area of 5  5 m2 was polarized with a 
constant voltage of record of  10 V according to the 
scheme "cantilever-film-substrate". By scanning in the 
mode of a kelvin probe microscopy on the bigger area of 
a film – 10  10 m2, the high level of polarization was 
established (Fig. 6). 
 
 
 
Fig. 6 – Spatial distribution of surface potential for the polar-
ized BTO at the record with voltage: left – 10 V and right – 
+ 10 V 
 
The observed "dark" and "light" areas correspond to 
ferroelectric domains with the polarization vector di-
rected from a probe and to it, respectively. Spatial lo-
calization at the record was comparable to the radius of 
the cantilever probe with the conducting covering 
 100 nanometers. 
Thus, optimum parameters of the stabilized BTO 
sedimentation were set by the LB method; the influ-
ence of a substrate on the structure of the created BTO 
films is studied. The polarization of the coverings ob-
tained which is characterized by high level of both con-
trast and spatial localization is found. 
 
 
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An Analysis of the Deposition Process and the Structure of Ferroelectric Langmuir Films of Barium Titanate

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An Analysis of the Deposition Process and the Structure of Ferroelectric Langmuir Films of Barium Titanate

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SocioEconomic Challenges Journal (Sumy State University)