TECHNICAL FIELD

The present invention relates to a method for the deposition of a material on a substrate, a method of manufacturing an electronic device and an electronic device. BACKGROUND OF THE INVENTION

The ferroelectric materials of perovskite family (Bai_ _x Sr _x )Ti0 ₃ (BST) have a very high dielectric constant, low dielectric loss, a very large "energy gap" and good structural stability. These substances prove to be the perfect materials for a wide range of applications including "dynamic random access memory (DRAM) , microwave phase shifters, integrated circuits for microwave and millimeter- range electro-optical devices. Other applications include switches and optical switches, planar waveguides, non-cooled infrared detectors and, above all, the super-capacitors for storage of electricity.

Thin films of BST for the various possible applications should be as homogeneous, uniform and of smooth surface (a small roughness at the nanoscale)as possible.

Recently, several methods have been tried for the preparation of BST thin layers of different methods including DC and RF "magnetron sputtering", methods of wet chemical process as the "sol-gel" and metalorganic chemical vapor deposition (MOCVD) . The pulsed laser ablation ( PLD) has, until now, demonstrated as a method suited to the growth of epitaxial thin films of BST. The advantages of PLD can be summarized in the following points :

• the composition of the target is transferred to the substrate without modification;

· The relatively high pressure (controllable) of the oxygen in the deposition chamber ensures efficient oxidation of the ablated material;

• the deposition temperature can be lower than in other methods because the arrangement of the material deposited on the substrate is helped by the high energy with which the ablated material is deposited.

The PLD method suffers from the important disadvantage of producing large amounts of particulate matter (particle size between 0.1 and 10 pm) that is deposited on the substrate, significantly and adversely affecting the electrical and optical properties of thin film thus obtained.

In the article "Pulsed electron beam deposition of oxide thin films" by Nistor et al . [J. Phys . D: Appl . Phys. 41 (2008)

165205 (lip)] is proposed the use of a pulsed electron deposition (PED) for the application of BST materials on substrates .

Nevertheless, this article does not provide sufficient information to allow effectively to obtain a layer of good quality BST (sufficiently smooth, homogeneous and free of impurities) .

The aim of the present invention is to provide a method for the deposition of a layer of material, a method for the construction of an electronic device and an electronic device, which allow to overcome, at least partially, the problems of the prior art and possibly are at the same time cheap and easy implementation.

SUMMARY

The present invention provides a method of depositing a layer of a material, a method of manufacturing an electronic device and an electronic device in accordance with the following independent claims and preferably with any of the dependent claims directly or indirectly of the independent claims .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below with reference to the annexed drawings, which illustrate some non-limiting examples of implementation, in which:

- Figure 1 shows schematically and partly in section of an apparatus that can be used in a method in accordance with the present invention;

- Figure 2 schematically shows a different embodiment of the apparatus of Figure 1;

- Figures 3, 5 and 7 show different phases of the implementation of a method in accordance with the present invention;

- Figures 4, 6 and 8 show various stages of implementing a method in accordance with the present invention;

- Figure 9 is a photograph SEM (scanning electron microscope) of a layer obtained by a method in accordance with the present invention; - Figure 10 is an optical spectrum of a "plum" obtained during the application of a method in accordance with the present invention;

- Figure 11 shows an image AFM (atomic force microscope) three-dimensional (a) and two-dimensional (b) a layer obtained by a method in accordance with the present invention;

- Figure 12 is an XRD spectrum of a layer obtained by a method in accordance with the present invention.

FORMS OF IMPLEMENTING THE INVENTION

In Figure 1, with 1 as a whole is shown an apparatus for the deposition of a material having a specific composition (Bai- _x Sr _x) Ti0 ₃ , where x ≤ 0 ≤ 1 (BST) by pulsed plasma deposition (Pulsed Plasma Deposition - PPD) . The apparatus 1 comprises a device 2 for plasma generation (that is to say at least partial ionization of a rarefied gas) and to direct a flow (pulsed) of electrons at a target 3, which shows (in particular consists of) the given material, so that at least part of the given material separated from the target 3 deposits on a surface of a substrate 4.

The target 3 and the substrate 4 are located inside a chamber 24 outside the apparatus 1, which also comprises a heating unit HU for heating the substrate 4. According to some embodiments, the heating of the substrate 4 is achieved by irradiation with infrared rays . Advantageously, the heating of the substrate by heating a back portion of 4 (in particular heating surface 4 opposite to the surface of the substrate) . In this regard, note that the substrate 4 is located between the heating unit and the target 3.

During the deposition of the given material (BST),the substrate 4 is maintained at a temperature of deposition from 400°C to 800°C. Advantageously, during the deposition, the substrate 4 is maintained at a temperature of deposition greater than 525 °C (more precisely, more than 600°C) . According to some embodiments, the substrate 4 is maintained at a temperature of deposition from about 650°C to about 750°C.

In this way, the given material (BST) is able to acquire a crystalline conformation during the deposition on the substrate 4.

Advantageously, the substrate 4 comprises a layer 4a (Figures 3 and 4) of a crystalline material with its 0001 hexagonal crystal plane substantially parallel to the surface 4' of the substrate. According to some embodiments, the substrate 4 is formed by the aforementioned crystalline material .

Advantageously, the crystal plane 0001 of the hexagonal crystalline material has a length of 0.45 nm to 0.49 nm (in particular, from 0.46 nm to 0.48 nm) . In other words, the crystal plane 0001 of the crystalline material has a hexagonal symmetry, whose side has the dimensions specified above .

More precisely, the crystalline material is sapphire.

The length of the faces (crystals) of the crystalline material are measured by means of X rays . According to some embodiments, the crystalline material is located in the area of the surface 4' . In other words, the crystalline material defines the surface 4' .

Note that the particular structure of the substrate 4 permits growth of the given material surprisingly epitaxial with respect to the crystalline material, in particular, with the crystal plane of Ill-type substantially parallel to the crystal plane 0001 of the layer 4a.

According to some embodiments, the substrate 4 comprises a layer 4b (Figures 3 and 4), which is placed at the surface 4' . The layer 4b comprises (in particular consists of) platinum. More precisely, the layer 4b define the surface 4' . In this case, advantageously, before the deposition of the given material (BST) , the substrate 4 is maintained at a temperature above the deposition temperature (up to 50°C higher than the temperature of deposition) for a period of at least 1 hour 30 minutes. Advantageously, the platinum layer 4b has the Ill-type crystal plane substantially parallel to the surface 4' (thus parallel to the face 0001 of crystalline material) .

In this way it is possible to obtain a more even distribution of platinum in the layer 4b.

Note that the layer 4b has a typical thickness of less than 200 nm (in particular from about 40 nm to about 200 nm, more precisely, from about 80 nm to about 140 nm) . According to specific embodiments, the layer 4b has a thickness from about 90 nm to about 110 nm. According to the embodiment shown in Figure 3, the layer 4b is deposited in contact with the layer 4a.

Advantageously, the substrate 4 comprises (below and in contact with layer 4b) layer 4c (Figure 4), which is located on the layer 4a (in contact) . The layer 4c comprises (in particular consists of) a further material with composition (Bai-y Sr _y )Ti0 ₃ wherein y < 0 < 1 (BST) . According to some embodiments, the given material and the further material are identical to each other.

Note that the layer 4c typically has a thickness less than

150 nm (in particular, from about 20 ran to about 150 nm, more precisely, less than 100 nm) . According to specific embodiments, the layer 4c has a thickness from about 30 nm to about 40 nm.

The layer 4c thermally and mechanically stabilizes the layer 4b.

The layers 4b and/or 4c are deposited by magnetron sputtering on the layer 4a. According to alternative embodiments, 4b and 4c are the layers deposited by other techniques such as pulsed plasma deposition (PPD) or wet chemical methods .

Note that, in any case, the layer 4b (and/or layer 4c) is surprisingly deposited in a substantially ordered way with the Ill-type crystal plane substantially parallel to the 0001 crystal plane crystal of the layer 4a.

Starting from the substrate 4 shown in Figure 3 (where the substrate 4 has layers 4a and 4b) the product Pi shown in Figure 5 is obtained by pulsed plasma deposition (PPD) of a layer 4d of a given material

Starting from the substrate 4 shown in Figure 4 (where the substrate 4 has layers 4a, 4b and 4c), the product P2 shown in Figure 6 is obtained by pulsed plasma deposition (PPD) of a layer 4d of the given material (BST) .

It is important to point out that, however, the layer 4d is surprisingly deposited in a substantially ordered way with the 111-type crystal plane substantially parallel to the surface 4" (in particular, to the 0001 crystal plane of the layer 4a and/or to the crystal plane 111 of the layer 4b) .

Note that using the method of the present invention it is possible to deposit a relatively thin layer 4d of a thickness less than 0.4 μπι. Advantageously, the layer 4d has a thickness less than 0.3 μπι. Note that it is possible to get a layer 4d with a thickness up to about 0.05 μιτι.

The layer 4d is crystalline and very homogeneous and substantially free of pin holes.

These features of the layer 4d significantly improve its electrical and optical properties.

The apparatus 1 also comprises a cover element C movable between an operating position (shown dashed) and a rest position (shown in solid line) .

In use, before the beginning of the deposition of the material on the specific substrate 4, the target 3 is cleaned. A beam (pulsed) of electrons (generated by the device 2) is directed against the target 3 so that the surface layer (on which the impurities can be deposited potentially) of the target 3 itself is removed and its particles are intercepted by cover element C (placed in its operational position) .

Once the target 3 has been cleaned it is possible to proceed with the deposition of the given material (BST) on the substrate 4 so as to obtain a higher quality layer 4d. During the deposition, the cover element C is maintained in its rest position to allow the particles of the given material to deposit freely on the surface 4'.

Advantageously, the target 3 is connected to ground. In this way, the target 3 does not reject (and indeed attracts) the flow of electrons even in the case that the electrons have already hit the target 3 itself.

The device 2 includes a hollow element 5, which acts as a cathode and has (externally delimits) internal cavity 6; and an activation electrode 7, which includes (in particular, consists of) an electrically conductive material (especially metal) . The activation electrode 7 is located within the cavity 6 (defined by the hollow element 5) . In particular, the hollow element 5 comprises (more specifically, it consists of) an electrically conductive material (more specifically a metal) .

In particular, electrically conductive material (eg. Stainless Steel, Tungsten, Molybdenum, Chromium, Iron, Titanium) means a material that has an electrical resistivity (measured at 20 °C) lower than 10 ^"1 Ω-m. Advantageously, the electrically conductive material has an electrical resistivity (measured at 20 °C) less than 10 ^~3 Ω-m.

The activation electrode 7 extends through a wall 8 of the hollow element 5. Between the activation electrode 7 and the wall 8 is interposed a ring 9 of substantially electrically insulating material (especially ceramics) .

In particular, substantially electrically insulating material means a material that has an electrical resistivity (measured at 20 °C) higher than 10 ³ Ω-m. Advantageously, the electrically non-conductive material has an electrical resistivity (measured at 20 °C) higher than 10 ⁷ Ω-m (more advantageously, more than 10 ⁹ Ω-m) . According to some embodiments, substantially electrically insulating material is a dielectric material.

The device 2 also includes a resistor 10, which connects the activation electrode 7 to ground and has a resistance of at least 100 ohms, advantageously at least 1 kOhm. In particular, the resistor 10 has a resistance of about 20 kOhm.

Inside the cavity 6 is a rarefied gas . According to some embodiments, the cavity contains the rare gas at a pressure less than or equal to 10 ^"2 mbar (in particular, less than 10 ^"3 mbar) . Advantageously, the rarefied gas contained within the cavity 6 has a pressure less than or equal to 10 ^"4 mbar. In particular, the rarefied gas contained within the cavity 6 has a pressure greater than or equal to 10 ^"6 mbar (more specifically, greater than or equal to 10 ^~5 mbar) . In this regard, note that the apparatus 2 comprises a group of gas supply (which in itself is known and not shown) to feed an anhydrous gas, (non-exhaustive examples - oxygen, nitrogen, argon, helium, xenon, etc.) inside the cavity 6 via a conduit 23.

The hollow element 5 is electrically connected to an activation assembly 11 which is adapted to decrease the electrical potential of the hollow element 5 of at least 4 kV (in particular, from an electrical potential substantially equal to zero) in less than 20 ns directing a pulse of electrical charge of at least 0.16 mC to the hollow element 5 itself. Advantageously, the activation assembly 11 is chosen in such a way to impose a reduction of potential to the hollow element 5 from 8 kV to 35 kV (more precisely, to 25 kV) in less than 15 ns, in particular in about 10 ns . The hollow element 5 is connected to ground. In this way, when the flux of electrons is not carried out, the hollow element 5 is maintained at substantially zero potential and the risk of spontaneous activation of the discharges between the hollow element 5 and the electrode 7 is substantially canceled.

In particular, a resistor 12 is connected between the hollow element 5 and ground. According to some embodiments, the resistor 12 has a resistance of 50 kOhm. Advantageously, the resistor 12 has a resistance of at least 100 kOhm, particulary about of at least 0.5 MOhm. According to some embodiments, the resistance is less than 1 MOhm. The activation assembly 11 includes a thyratron 13, a capacitor 14 which has one armature connected to an anode 15 of the thyratron 13 and the other armature connected to the hollow element 5, and a power supply 16, which has a positive electrode 17 electrically connected to anode 15 and a negative electrode 18 connected to ground.

The thyratron 13 also has a cathode 19, which is connected to ground.

Note that the capacitor 14 is electrically connected to ground (in particular, through the resistor 12) .

The activation assembly 11 also includes a control unit 20 of the thyratron 13 , which is capable of operating the thyratron 13 and is connected to ground.

The device 2 also comprises an operator interface assembly (known per se and not shown here) , which allows an operator to adjust the operation (for example switching on and/or modification of operating parameters) of device 2 itself.

The device 2 also comprises a tubular element 21, which includes (in particular, is) a substantially electrically insulating material (in particular glass, quartz or alumina) and is connected to the hollow element 5. The tubular element 21 has two open ends 21a and 21b and an inner opening which connects the cavity 6 with the outside space (in particular, with the outer chamber 24) .

The hollow element 5 (except of the conduit 23 and the tubular element 21) is vacuum-tight to the outside.

The tubular element 21 extends at least partially within the outer chamber 24 (Figure 1), where the target element 3 and the substrate element 4 are arranged in. The tubular element 21 and its inner opening have, respectively, substantially circular cross sections.

Inside the outer chamber 24 is present a rarefied gas (according to some embodiments, anhydrous) . According to some embodiments, the cavity contains the diluted gas at a pressure less than or equal to 10 ^"2 mbar (in particular, less than 10 ^"3 mbar) . Advantageously, the diluted gas contained within the outer chamber 24 is maintained at a pressure less than or equal to 10 ^"4 mbar using a pumping device (of a known type and not shown) . In particular, the diluted gas contained within the outer chamber 24 has a pressure greater than or equal to 10 ^~6 mbar (more specifically, greater than or equal to lC ⁵ mbar) . Advantageously, the gas is oxygen.

The pressure (from about 5xl0 ^"4 mbar to about 1CT ² mbar) inside the cavity 6 is maintained (slightly) higher than that present in the outer chamber 24 (in particular, feeding small amounts of gas through a duct 23) .

According to the embodiment shown in Figure 1, the tubular element 21 extends through a wall 22 of the hollow element 5 (opposite to the wall 8), partly inside and partly outside of the cavity 6 (in particular, inside of the outer chamber 24) .

According to specific embodiments, the tubular element 21 has a length of 90 mm to 220 mm. The tubular element 21 has a diameter of about 4 mm to 10 mm. The inner lumen 21c has a diameter from about 1.5 to about 8 mm. The outer chamber 24 is constructed to be vacuum-tight relation to its surroundings .

According to specific embodiments the target 3 and substrate 4 are arranged at a distance of 35 mm to 65 mm (more precisely, from 40 mm to 60 mm) . The distance between the target 3 end an edge 21b is between 1 and 20 mm (more precisely, between 3 and 8 mm) .

The device 2 also includes an external element 25 which is located outside of the hollow element 5 (in particular, in the outer chamber 24) along the tubular element 21 (i.e., not at one end of the element tube 21) and acts as an anode. In particular, the outer element 25 is placed in contact with an outer tubular element 21.

The outer element 25 is shaped so as to be arranged around tubular element 21, in particular, the outer element 25 has a hole through which extends the tubular element 21. According to specific embodiments, the outer element 25 has a n annular shape.

The device 2 also comprises a group 26 which maintains the electrical potential and which is electrically connected to the external element 25 to maintain the electrical potential of the external element 25 substantially grounded.

In use, the activation assembly 11 imposes a potential difference between the hollow element 5 and the activation electrode 7 according to the above parameters. As a result, the plasma is generated (that is to say at least partial ionization of the diluted gas) inside the cavity 6. When the electrons formed inside the cavity 6 enter the tubular element 21, the potential difference, which was established with the external element 25, allows electrons to be accelerated along the same tubular element 21 to the target 3. These electrons during its movement scatter to more gas molecules and determine, therefore, the emission of secondary electrons which, in turn, are accelerated toward the target 3.

According to specific embodiments, the device 1 and device 2 (except for what concerns the outer chamber 24 and its contents) of Figure 1 show a similar structure and operation of the apparatus and the device described in the application of PCTIB2010000644 patent.

Figure 2 shows an alternative embodiment of the device 2 and the apparatus 1. Components shown in Figure 2 which are similar to those shown in Figure 1 are denoted by the same reference number.

The device 2 of Figure 2 shows an ampoule 28 (usually glass) , outside of which the activation electrode 7 is placed; and a stabilization group 27 as described above. The capacitance of the capacitor 14 is also in this case as indicated according to the embodiment of Figure 1.

In use, the hollow element 5 is maintained at a relatively high negative electric potential (i.e., negatively charged - about 13-16 kV) and when an electrical pulse is produced on the activation electrode 7 it creates a glow discharge which, in turn, generates a positive electrical charge inside the hollow element 5. The positive charge is compensated by the emission of electrons, which in turn are accelerated towards the first element 25 inside the outer tube 21. The electrons moving outward ionize more molecules producing more electrons (called secondary electrons), which, in turn, are accelerated toward the target 3.

More precisely, the device 1 and device 2 (except for what concerns the outer chamber 24, its contents and the tubular element 21) of Figure 2 show a similar structure and operation of the apparatus and the device described PCTEP2006003107 in the patent application of the applicant.

According to some non-shown embodiments, the device 1 and device 2 (except for what concerns the outer chamber 24 and its contents) have a similar structure and function (with an appropriate adjustment of operating parameters) to equipment and devices described in Italian patent application BO2010A000525 of the same applicant.

According to a further aspect of the present invention, a method is provided for the creation of an electronic device 30. In particular, the device 30 is an electronic capacitor (two embodiments are shown in Figures 7 and 8) . To obtain the device 30 a layer 4d as described above and further layer 4e comprising (in particular, consisting of) platinum are deposited on the layer 4d. Again, the deposition is carried out with PPD. Alternatively, the deposition of the fourth layer is made by magnetron sputtering.

Note that the layer 4e has typically a thickness less than 200 nm (in particular from about 40 nm to about 200 nm, more specifically, from about 80 nm to about 140 nm) . According to specific embodiments, layer 4e has a thickness from about 90 nm to about 110 nm.

In this way (starting with the P2 shown in Figure 6), we obtain a device 30 (Figure 8) comprising a layer 4a, a layer 4b, a layer 4e, a layer 4c interposed in contact between the layer 4a and layer 4b , and a layer 4d interposed in contact between the layer 4b and layer 4e.

According to various embodiments, (starting with the Pi shown in Figure 5), we obtain a device 30 (Figure 7) comprising a layer 4a, a layer 4b, a layer 4e and a layer 4d interposed in contact between the layer 4b layer and 4e.

More precisely, the device 30 includes an electric contact

31, which is connected to the layer 4b, and electrical contact 32, which is connected to the layer 4e.

The contact layer 31 is deposited substantially simultaneously with the deposition of the layer 4b. The contact 32 is deposited on the layer 4d substantially simultaneously with the deposition of the layer 4e.

Note that using the method of the present invention it is possible to obtain the layer 4d with a thickness up to about

Based on the above it is clear that with the method of the present invention it is possible to produce a layer 4d with very low thickness, substantially crystalline, substantially free of holes (pin holes) and with a high degree of purity. In this regard, note that a high degree of crystallinity contributes to expel impurities, and that the presence of impurities can lead to discharge between the layers 4b and 4e. In addition, the pin holes put in direct contact layers 4b and 4e determining, during operation of the device 30, the burning of the device 30 itself. These advantages are obtained with a layer 4d (BST) thin and therefore reduce the overall dimensions and greatly increase the electrical capacity of the device 30 and also exhibit low production costs .

Unless explicitly stated otherwise, the contents of references (articles, books, patent applications, etc.) cited in this text are herein recalled in their entirety. In particular, the mentioned references are incorporated herein by reference.

Additional features of the present invention will result from the following description of two examples merely illustrative and not restrictive.

Example 1

Preparation of substrates

Sapphire substrates were prepared from single-crystal plates of dimensions 10 x 5 x 0.5 mm with the crystal plane 0001 oriented in parallel with the largest surface.

They were chosen two types of deposition surface preparation: on the deposition surface of the first "batch" of substrates has been pre-deposited a thin layer of platinum (about 100 nm) (Figure 3) by the method of "magnetron sputtering" as one of the conductors of the future capacitor and, simultaneously, an electrical contact. A thin layer of BST (about 30 to 40 nm) and then a thin layer of platinum (about 100 nm) (Figure 4) has been pre- deposited by the method of magnetron sputtering on the surface of the second "batch" of substrates . In both cases the layer of platinum is grown in an ordered and oriented way with the crystal planes of type 111 parallel to the plane 0001 of the substrate (and therefore parallel with the surface deposition) .

Before the deposition the substrates were cleaned in ultrasonic bath of acetone for 10 min, rinsed with methanol (spectroscopic grade) and then with distilled water. Once dried using a stream of pure nitrogen (5 PA) were subjected to treatment with argon plasma (plasma power P = 100 W, gas pressure in the chamber p = 6 * 10 ^"1 mbar, time treatment t = 5 min.). Immediately after the plasma treatment substrates were transported in a deposition chamber (outer chamber) . Here were mounted on a rotating sample holder heated by the infrared system. The distance between the substrate and the target of BST _; from which is then ablated the deposited material, was set to 48 mm. All the deposition system was closed and taken to the base pressure (1 * 10 ^"6 mbar) at room temperature for a period between 2 and 12 hours before the deposition.

Example 2

Deposition of BST

The substrates prepared according to the example above, were heated in the range between 650 - 700 °C. The heater was set to rotate with the frequency ca. 0.1 Hz, gas pressure inside the deposition chamber was increased to 2.6 * 10 ^~3 mbar and kept at this value throughout the period of deposition.

As a cannon the device 2 as shown in Figure 2 (ie as described in the patent application PCTEP2006003107 of the applicant has been used. The voltage of the gun has been selected in the range between 14 kv and 25 kV. The voltage of 25 kv was judged the most suitable.

The rotating target (rotated with a frequency of approximately 0.3 Hz) was subjected to an ablation under the same conditions of deposition as described below for a period of about 30 minutes, but the ablated material was intercepted with a cover element and did not arrive to the substrate. This process - the conditioning of the target - ensures the same properties of the target deposition for each event and for any previous history of the target.

After conditioning of the target, the cover element is removed and the ablated material begins to deposit on the substrate .

The ablation rate (the rate of discharge of the gun) was varied between 1 Hz and 50 Hz, the frequency was selected between approx. 35 and 45 Hz (in particular, 40 Hz) . The quality of the "plum" (which is defined by the trajectories of particles that are separated from the target) generated by the PPD ablation of BST was checked by measurements of the optical spectrum (Figure 10, the abscissa shows the wavelength in nm, the ordinate exhibits an intensity in arbitrary units) . The characteristic time of the deposition was chosen in the range between 15 and 120 min. The optimal duration of deposition was approximately 30 min.

The layers of BST of about 0.1 (0.2) μ m thick were obtained in this way.

Example 3

Results of the deposition mentioned in example 2.

It has been observed the importance to precede the deposition of BST materials with thermal pretreatment of the substrate. Without pretreatment the thin layer of platinum tends to aggregate into separate islands higher then the original film during the deposition, especially in the case of substrates without coating by "intermediate" layer of BST. In this way the layer of BST has been damaged due to the underlying layer of platinum and shows small holes ('pin-holes ") visible by optical microscopy.

The thermal pretreatment consists of a heating of the substrate held in a vacuum at the temperatures higher from 0 to 50 °C than deposition temperatures about 2 hours. This process stabilizes the layer of platinum and the "pin-holes" in the deposited film does not open any more later.

The data given below (and the related photo) were obtained using the pre-heated substrates.

The morphology of the deposited BST films is shown in Figure 9. The layer is composed of a dense aggregation of grains of BST. The average size of grains is approx. 150 nm. Note the particulate on the surface layer of the characteristic size approx. 10 to 20 nm. The average lateral grains size of 150 nm is substantially larger than the roughness of the film (about 15 to 25 nm rms) , as shown in Figure 11 which shows the AFM images (Atomic Force Microscopy) of the surface - Figure 11a - and the single scan - Figure lib. This fact shows that the BST layer grows with a preferred orientation parallel to the substrate surface in an almost-epitaxial way. The same conclusion can be drawn also from the X-ray difractogram shown in Figure 12 [x-axis shows the fraction of 2theta angle (deg) , the ordinate shows the X-ray intensity in arbitrary units] .

In the Figure 11 (a) (bottom right corner) it can bee seen the presence and morphology of a "pin-hole" in the film. The "pin-hole" has been obtained by using the substrate which was not clean according to the procedure above.

The X-ray difractogram (Figure 12) shown in Figure 12 shows how the structure matches that of the crystalline structure of BST material (the maximum intensity at diffraction angles 2Θ around 39.7 and 67.5 degrees correspond to the reflections of the substrate) . The relative intensities of maximum diffraction corresponding to the crystalline structure of BST suggest that the BST layer grows preferentially oriented with the 111 crystal plane parallel to the substrate surface.

The measurements of the electrical characteristics revealed that the BST thin films prepared by the PPD method mentioned above reach the value of the dielectric constant between 600 and 1000.