Photochemical Metal-organic Deposition Research Articles

Effects of UV-irradiation during photochemical metal-organic deposition on the electric and ferroelectric properties of direct-patternable Bi 3.25La 0.75Ti 3O 12 films

The electric and ferroelectric properties of UV-irradiated and non-irradiated Bi 3.25La 0.75Ti 3O 12 (BLT) films prepared by photochemical metal-organic deposition using photosensitive precursors were characterized. Fourier transform infrared spectroscopy showed that complete removal of organic groups was possible through ultraviolet exposure of the spin-coated BLT precursor films at room temperature. The measured remnant polarization values of UV-irradiated and non-irradiated BLT films after annealing at 700 °C were 16.0 and 10.1 µC/cm 2, respectively. The process of UV-irradiation was effective for the enhancement of electric and ferroelectric properties, as well as direct-patterning to fabricate micro-patterned systems without dry etching.

Fabrication and Characterization of Direct-patternable PZT Film Prepared by Photochemical Metal-organic Deposition

The ferroelectric properties of UV irradiated and non-irradiated PZT films prepared via photochemical metal-organic deposition using photosensitive precursors were characterized. Fourier transform infrared spectroscopy showed that complete removal of organic groups was possible through UV exposure of the spin-coated PZT precursor films at room temperature. The measured remnant polarization values of UV- irradiated and non-irradiated PZT films after annealing at 650 C were 29 and 23 µC/cm , respectively. The UV irradiation was found to be effective for the enhancement of the growth orientation and ferroelectric property of PZT film and in the direct patterning in the fabrication of micro-patterned systems without dry etching.

Electric and ferroelectric properties of PZT/SBT multilayer films prepared by photochemical metal-organic deposition

Abstract The electric and ferroelectric properties of lead zirconate titanate and strontium bismuth tantalate multilayer films prepared using photosensitive starting precursors were characterized. The electric and ferroelectric properties were investigated by characterization of the effect of stacking order of four ferroelectric layers of PZT or SBT in the multilayer films of 4-PZT, PZT/2-SBT/PZT, SBT/2-PZT/SBT, and 4-SBT. The Pr value of the 4-SBT multilayer film was relatively small (6 μC/cm2) and a two times higher value (12 μC/cm2) was obtained with the SBT/2-PZT/SBT multilayer film. The films with SBT layers at the top and bottom showed improved leakage current and fatigue resistance compared to the films with PZT layers at the top and bottom. It was revealed that the defect dipole was reduced at the SBT/Pt interface due to a self-regulation layer such as (Bi2O2)2+ in the SBT film. Also, the bottom layer on the Pt substrate showed a significant influence on the growth orientation of the entire ferroelectric films.

Study of Ag nanoparticles incorporated SnO 2 transparent conducting films by photochemical metal–organic deposition

Ag nanoparticles with a narrow size distribution were prepared by spontaneous reduction of Ag 2-ethylhexanoate in dimethyl sulfoxide. According to the incorporation content, SnO 2 film transmittance was slightly reduced by light absorption of incorporated Ag nanoparticles. With incorporation of Ag nanoparticles, the crystallinity of the SnO 2 films slightly decreased and the film sheet resistance improved. The valence band maximum of SnO 2 films containing Ag nanoparticles indicated a shift towards the Fermi energy level, corresponding to an increase of electrons in the valence band from electron transfer from the Ag nanoparticles to the film. Direct-patterning of SnO 2 films with Ag nanoparticles was produced without photoresist or dry etching. These results suggest a micro-patterned system can be simply fabricated with low cost and the electrical properties of the SnO 2 films can be improved by incorporating Ag nanoparticles.

Study on the Electrical Properties of Direct-Patternable SBT Films Formed by Photochemical Metal-Organic Deposition

The ferroelectric properties of UV irradiated and non-irradiated SBT thin films using photosensitive starting precursors were investigated. The observation of surface microstructure showed that UV irradiation and increase in anneal temperature induced the grain growth of SBT. The measured remnant polarization values of UV irradiated and non-irradiated SBT films after anneal at 700oC were 5.8 and 4.7 )C/cm2 and after anneal at 750oC, the values were 10.8 and 9.3 )C/cm2, respectively.

Photoresist Free Negative and Positive Photolithographic Deposition of Zirconium Oxide Films from Photosensitive Metal Organic Compounds

ABSTRACTPhotoresist free photolithographic deposition of zirconium oxide from photosensitive zirconium complexes has been achieved using photochemical metal organic deposition. In this contribution, the deposition of patterned zirconium oxide is used as an example to demonstrate both negative and positive photolithographic deposition. In the prototypical deposition of zirconium oxide by photochemical metal organic deposition, a solution containing zirconium (IV) di-n-butoxide bis(2, 4-pentanedionate) was used to spin coat a silicon substrate, resulting in an amorphous film. The film was then exposed to UV light leading to the formation of zirconium oxide and other volatile products. The resultant zirconium oxide film was investigated by X-ray diffraction and Auger Electron Spectroscopy. Irradiating the precursor film through a photo mask led to a latent image which yielded either a negative or a positive pattern dependent upon developer. Subject to further photochemical or thermal treatment, a zirconium oxide pattern can be obtained. Similar results were obtained using a series of zirconium (IV) complexes. Both positive and negative patterns of zirconium oxide with 2 micron feature sizes were obtained.

Magnetic properties of nanocrystalline iron oxide/amorphous manganese oxide nanocomposite thin films prepared via photochemical metal-organic deposition

Maghemite (γ-Fe2O3) nanocrystals have been prepared by the thermal decomposition of metal-organic precursors in the presence of oleic acid. These nanocrystals were characterized by transmission electron microscopy, SQUID magnetometry, and Mossbauer spectroscopy. Samples of maghemite nanocrystals with a median diameter of 4 nm were found to be superparamagnetic, with a blocking temperature of ca. 36 K. These nanocrystals were encapsulated in an amorphous manganese oxide matrix by means of photochemical metal-organic deposition. In this process, solutions containing γ-Fe2O3 nanocrystals and manganese(II) 2-ethylhexanoate were spin coated on silicon substrates. Upon irradiation, the photosensitive manganese precursor undergoes decomposition, leaving a manganese oxide thin film containing dispersed nanocrystals. Photoresist-free lithographic deposition of micron-sized features composed of the γ-Fe2O3 nanocrystals/amorphous manganese oxide nanocomposite was carried out. The magnetic properties of the nanocomposite thin films were measured, and shown to bear differences with the bulk nanocrystals. In particular, the blocking temperature is lowered with increased nanocrystal dilution. The magnetic properties of the system are discussed in terms of clusters of strongly interacting superparamagnetic nanocrystals.

Electrical and ferroelectric properties of SBT thin films formed by photochemical metal-organic deposition

The electrical and ferroelectric properties of SBT thin films prepared by photochemical metal-organic deposition using photosensitive starting precursors were characterized. Fourier transform infra-red spectroscopic observation showed that a complete removal of organic groups was possible by UV exposure of spin-coated SBT precursor film at room temperature. The values of measured remnant polarization and leakage current density at 400 kV/cm were 5.8 μC/cm 2 and 3.48 × 10 −8 A/cm 2 after anneal treatment at 700 °C of the UV-exposed SBT precursor film and 10.8 μC/cm 2 and 6.94 × 10 −8 A/cm 2 after anneal treatment at 750 °C. The SBT films annealed at 700 and 750 °C remained fatigue-free up to 10 10 switching cycles.

Electrical properties of PLZT thin films formed by photochemical metal-organic deposition with various Zr/Ti ratios

Lanthanum-doped lead zirconate titanate (PLZT) films formed by photochemical metal-organic deposition using photosensitive starting precursors were characterized. The substitution of La for Pb was found to induce the improved ferroelectric properties, especially fatigue property through the reduction of oxygen vacancies with excess electrons. But remnant polarization was reduced, because the doping of La gives the same effect as shift of composition of Zr/Ti ratio in PLZT film from morphotropic phase boundary composition of PZT(Zr/Ti ratio of 56/44). The measurement results of polarization-electric field and capacitance-voltage indicate that the composition of maximum ferroelectric properties of PLZT film shifts toward Ti-rich side between 52/48 and 48/52 of Zr/Ti ratio. A decrease in Zr/Ti ratio induced an improvement in I-V and fatigue properties due to the low defect concentration such as Pb or O vacancies and the inter-grain depletion of grain boundary limited conduction.

Direct-patterning of SnO 2 thin film by photochemical metal-organic deposition

The optical and electrical properties were characterized with direct-patternable SnO 2 thin film prepared by photochemical metal-organic deposition (PMOD) using photosensitive starting precursors. Fourier transform infrared spectroscopic analysis showed that a complete removal of organic groups was possible by an exposure of spin-coated SnO 2 precursor film to UV at room temperature. According to the increase in anneal temperature, i.e., amelioration in the crystallinity and structural homogeneity of SnO 2 film, optical transmission and resistivity improved; especially in case of optical transmission, there was also an effect from the decrease in film thickness. Direct-patternable SnO 2 film annealed at 800 °C showed the values of average transmittance in visible region and resistivity as 92.28% and 1.61 × 10 −2 Ω cm, respectively.

Positive and Negative Lithography by Photochemical Metalorganic Deposition from Metal 2-ethylhexanoates

Direct, resist-free positive photolithographic deposition of various metal oxides was achieved using photochemical metalorganic deposition. The metalorganic precursors, manganese(II) 2-ethylhexanoate, nickel(II) 2-ethylhexanoate and molybdenum(II) 2-ethylhexanoate and mixtures of barium(II) 2-ethylhexanoate and titanium(IV) di-n-butoxide bis(2-ethylhexanoate), were all spin cast as amorphous thin films from solutions. Upon exposure to ultraviolet light, the organic components of the precursor are ejected from the film and the remaining metal is ultimately converted to amorphous metal oxide or mixed metal oxide. The photochemistry of the decomposition reaction of all precursors was monitored by Fourier transform infrared spectroscopy. Upon exposure to UV light irradiation, negative photolithography was observed. However, after a short period of exposure to UV light, positive pattern of the precursor can be developed. When this process is followed by a blanket exposure, the net result is the positive lithographic deposition of the metal oxide. By using these precursors and contact photolithography, the deposition of micron sized features of amorphous manganese, nickel and molybdenum oxide, and Ba1.13T0.17O was achieved, in both the negative and positive lithography methods.

Positive and Negative Photolithographic Deposition of Titanium Dioxide from Photosensitive Titanium Complexes

Lithographic deposition of titanium oxide films using photochemical metal organic deposition from titanium (IV) complexes is demonstrated in this paper. In this paper we explore the chemistry of thin films of titanium (IV) di-n-butoxide bis(2-ethylhexanoate), titanium (IV) di-n-butoxide bis(2-ethyl-2-hydroxybutyrate), titanium (IV) diisopropoxide bis(2,4-pentanedionate), and titanium (IV) diisopropoxide bis(ethyl acetoacetate). These complexes could all be prepared by ligand exchange reaction from the appropriate precursors. Thin films of each of these compounds could be cast by spin coating from solutions. All the complexes underwent photodecomposition to form titanium dioxide films although only titanium (IV) di-n-butoxide bis(2-ethylhexanoate) did so without the formation of an intermediate. Since all of the precursors were soluble negative lithography resulted in the direct deposition of titanium dioxide from these precursors. In contrast we were only able to demonstrate positive lithography on all the films except those constructed from titanium (IV) di-n-butoxide bis(2-ethylhexanoate). Positive lithography was conducted by exposing a region developing to remove film in the exposed regions followed by blanket exposure to convert the remaining regions to titanium dioxide. Patterns of titanium oxide with a feature size of 1 micron and a resolution of 1 micron were routinely achieved by both positive and negative photolithography. These precursors are also potential candidates for deep UV lithography in fabricating features of sub-50 nanometres.

Photochemical Metal Organic Deposition of Patterned Nanostructured Oxide Films

AbstractIn this paper, we present examples of the use of photochemical metal organic deposition to form nanostructured metal oxide films. In the first example, we use two reactions with very different reaction rates to control the nanostructuring, utilizing tantalum (V) tetraethoxide acetylacetonate (as a thermally reactive source of tantalum oxide) and manganese (II) 2-ethylhexanoate (as a photochemically reactive source of manganese oxide). We prepare homogeneous precursor films of tantalum (V) tetraethoxide acetylacetonate and manganese (II) 2-ethylhexanoate and in the dark allow the tantalum complex to react forming tantalum oxide regions. The film is then exposed and the manganese complex is converted to a matrix surrounding the tantalum regions. The resultant structures are characterized by electron microscopy, energy dispersive X-ray spectroscopy and Auger spectroscopy. In the second example, we use two immiscible precursors, zirconium (IV) 2-ethylhexanoate and yttrium nitrate hexahydrate to form nanostructured precursor films. The nanostructuring of these films is apparent from SEM studies. Exposure of these films results in the formation of nanostructured films consisting of a zirconium oxide matrix with encapsulated yttrium oxide.

Stacking effect on the ferroelectric properties of PZT/PLZT multilayer thin films formed by photochemical metal-organic deposition

The ferroelectric properties of lead zirconate titanate (PZT) and lanthanum-doped lead zirconate titanate (PLZT) multilayer films formed by photochemical metal-organic deposition (PMOD) using photosensitive precursors have been characterized. The substitution of La for Pb was reported to induce improved ferroelectric properties, especially fatigue resistance, through the reduction of oxygen vacancies. The relation between La-substitution and the ferroelectric properties was investigated by characterization of the effect of the order of stacking four ferroelectric layers of PZT or PLZT in the multilayer films 4-PZT, PZT/2-PLZT/PZT, PLZT/2-PZT/PLZT, and 4-PLZT. The films with the PLZT layer at the top and bottom showed an improvement in the fatigue resistance. It was revealed that defect dipole such as O vacancy was reduced at the ferroelectric/Pt interface by doping with La. Also, the bottom layer, just on Pt substrate had a significant influence on the surface microstructure and growth orientation of ferroelectric film.

Characterization of PLZT thin film prepared by photochemical deposition using photosensitive metal-organic precursors

The electrical properties of lanthanum doped lead zirconate titanate (PLZT) thin films prepared by photochemical metal-organic deposition (PMOD) using photosensitive starting precursors have been characterized. PLZT films with various La concentration were prepared by PMOD on Si(1 0 0) for observing the image of self-patterned PLZT film or on Pt(1 1 1)/Ti/SiO 2/Si(1 0 0) for ferroelectric properties measurement. Even though PLZT film with 0 mol% of La, strictly PZT, showed an asymmetric behavior in polarization-voltage ( P– E) relation, PLZT film by doping La showed symmetric behavior in P– E relation. The amelioration of electric and ferroelectric properties with increased substitution of La in PLZT film was observed, especially with 3 mol% La doped PLZT film, the most characteristic P– E hysteresis loop in the point of imprint property was obtained with comparatively large remnant polarization, 30 μC/cm 2 at 15 V. Also, capacitance and leakage current behavior of PLZT film were revealed to be sensitive to the contents of La.

Electrical properties of PZT thin films by photochemical deposition

The electrical properties of lead zirconate titanate (PZT) thin film prepared by photochemical metal–organic deposition (PMOD) using photosensitive starting precursors were characterized. Unlike sol–gel procedure based on the chemical reaction including hydrolysis and condensation, by PMOD, metallic state is obtained through the removal of organic ligand by exposure to UV. This metallic state usually turns to oxide state through oxidation reaction with atmospheric oxygen during exposure to UV. Fourier transform infra-red spectroscopic observation showed that a complete removal of organic group was possibly obtained by exposure of spin-coated PZT precursor film to UV at room temperature. After anneal treatment of the UV-exposed PZT precursor film to crystallize, a highly preferred growth orientation was found in PZT film according to the orientation of substrate Pt. The characteristics of ferroelectric properties (remnant polarization and coercive field) and leakage current behavior were almost the same as those of conventional PZT film prepared by sol–gel processing. However, a slight shift of hysteresis curve and more leaky behavior with negative direction of bias were found and it seemed to be due to the presence of micro-defects formed during PMOD reaction.

Electrical properties of PZT thin films by photochemical deposition

The electrical properties of lead zirconate titanate (PZT) thin film prepared by photochemical metal–organic deposition (PMOD) using photosensitive starting precursors were characterized. Unlike sol–gel procedure based on the chemical reaction including hydrolysis and condensation, by PMOD, metallic state is obtained through the removal of organic ligand by exposure to UV. This metallic state usually turns to oxide state through oxidation reaction with atmospheric oxygen during exposure to UV. Fourier transform infra-red spectroscopic observation showed that a complete removal of organic group was possibly obtained by exposure of spin-coated PZT precursor film to UV at room temperature. After anneal treatment of the UV-exposed PZT precursor film to crystallize, a highly preferred growth orientation was found in PZT film according to the orientation of substrate Pt. The characteristics of ferroelectric properties (remnant polarization and coercive field) and leakage current behavior were almost the same as those of conventional PZT film prepared by sol–gel processing. However, a slight shift of hysteresis curve and more leaky behavior with negative direction of bias were found and it seemed to be due to the presence of micro-defects formed during PMOD reaction.

PMODTM-based Direct Thin Film Imaging, DTFITM, on Flexible Substrates

AbstractPMOD (Photochemical Metal Organic Deposition)-based DTFI (Direct Thin Film Imaging) methodology is a demonstrated means for patterning organic materials on flexible (plastic) substrates. This process is used to pattern 1-micron features at an aspect ratio of 8:1 using contact lithography. Use of oxygen plasma RIE etch to transfer the hard mask pattern to the organic material allows for good sidewall angle control. High etch selectivity between the novolac polymer and PMOD TiOX hard mask (< 800:1) makes the use of very thin hard masks (∼ 200 angstroms) to pattern thick organic films (<10 microns) possible. Selective removal of the PMOD TiOX (TiO2) hard mask makes this process amenable to patterning of functional organic structures fabricated from materials chosen for their desired properties (e.g., glass transition temperature (Tg), etch resisitance, optical properties, mechanical properties, etc.) not their ability to be photopatterned (e.g., photoresist).

The mechanism of the photochemical metal organic deposition of lead oxide films from thin films of lead (II) 2-ethylhexanoate

A mechanistic study of the photochemistry of thin films of lead (II) 2-ethylhexanoate is presented. Films of lead (II) 2-ethylhexanote can be cast on silicon solutions by spin coating. Spectroscopic evidence suggests that the molecules are polymeric within the thin film. Irradiation of the film with ultraviolet light leads to the fragmentation of the complex and the ejection of carbon dioxide, heptane and heptene from the film. The quantum yield for the reaction of the lead complex was found to be within error of one. A mechanism consistent with these results is presented. The composition of the film remaining on the surface is approximately that of lead (II) oxide. Annealing resulted in the formation of crystalline PbO 1.37.

The photochemical metal organic deposition of manganese oxide films from films of manganese(II) 2-ethylhexanoate: a mechanistic study

The photochemistry of thin films of manganese(II) 2-ethylhexanoate to produce manganese oxide films is presented. Thin films of manganese(II) 2-ethylhexanoate can be cast onto silicon wafers by spin coating. The FTIR spectroscopy of these films suggests they exist as chains or clusters with the manganese(II) centers linked by bridging 2-ethylhexanoate ligands. The initial photochemical reaction results in the loss of the bridging 2-ethylhexanoate ligands and the formation of monomeric manganese(II) 2-ethylhexanoate. In this process approximately 60% of the bridging 2-ethylhexanoate ligand is converted to chelating 2-ethylhexanoate while the other 40% fragments to form CO 2, heptane and heptene. Further photolysis resulted in the conversion of the remaining 2-ethylhexanoate ligand to form CO 2, heptane and heptene. The film consisted of manganese(II) oxide although the surface of the film was more oxidized and had carbon impurity on it. Annealing the film resulted in the conversion to polycrystalline α-Mn 2O 3.