Transparent oxide semiconducting films have continued to receive considerable attention, from a fundamental and application-based point of view, primarily because of their useful fundamental properties. Of particular interest is zinc oxide (ZnO), an n-type semiconductor that exhibits excellent optical, electrical, catalytic and gas-sensing properties, and has many applications in various fields. In this work, thin film transistor (TFT) arrays based on ZnO have been prepared by reactive radio frequency (RF) magnetron sputtering. Prior to the TFT fabrication, ZnO layers were sputtered on to glass and silicon substrates, and the deposition parameters optimised for electrical resistivities suitable for TFT applications. The sputtering process was carried out at room temperature with no intentional heating. The aim of this work is to prepare ZnO thin films with stable semiconducting electrical properties to be used as the active channel in TFTs; and to understand the role of intrinsic point defects in device performance and stability. The effect of oxygen (O2) adsorption on TFT device characteristics is also investigated. The structural quality of the material (defect type and concentration), electrical and optical properties (transmission/absorption) of semiconductor materials are usually closely correlated. Using the Vienna ab-initio simulation package (VASP), it is predicted that O2 adsorption may influence film transport properties only within a few atomic layers beneath the adsorption site. These findings were exploited to deposit thin films that are relatively stable in atmospheric ambient with improved TFT applications. TFTs incorporating the optimised layer were fabricated and demonstrated very impressive performance metrics, with effective channel mobilities as high as 30 cm2/V-1s-1, on-off current ratios of 107 and sub-threshold slopes of 0.9 – 3.2 V/dec. These were found to be dependent on film thickness (~15 – 60 nm) and the underlying dielectric (silicon dioxide (SiO2), gadolinium oxide (Gd2O3), yttrium oxide (Y2O3) and hafnium oxide (HfO2)). In this work, prior to sputtering the ZnO layer (using a ZnO target of 99.999 % purity), the sputtering chamber was evacuated to a base pressure ~4 x 10-6 Torr. Oxygen (O2) and argon (Ar) gas (with O2/Ar ratio of varying proportions) were then pumped into the chamber and the deposition process optimised by varying the RF power between 25 and 500 W and the O2/Ar ratio between 0.010 to 0.375. A two-level factorial design technique was implemented to test specific parameter combinations (i.e. RF power and O2/Ar ratio) and then statistical analysis was utilised to map out the responses. The ZnO films were sputtered on glass and silicon substrates for transparency and resistivity measurements, and TFT fabrication respectively. For TFT device fabrication, ZnO films were deposited onto thermally-grown silicon dioxide (SiO2) or a high-k dielectric layer (HfO2, Gd2O3 and Y2O3) deposited by a metal-organic chemical deposition (MOCVD) process. Also, by using ab initio simulation as implemented in the “Vienna ab initio simulation package (VASP)”, the role of oxygen adsorption on the electrical stability of ZnO thin film is also investigated. The results indicate that O2 adsorption on ZnO layers could modify both the electronic density of states in the vicinity of the Fermi level and the band gap of the film. This study is complemented by studying the effects of low temperature annealing in air on the properties of ZnO films. It is speculated that O2 adsorption/desorption at low temperatures (150 – 350 0C) induces variations in the electrical resistance, band gap and Urbach energy of the film, consistent with the trends predicted from DFT results.

Les procédés de dépôt en phase vapeur sont particulièrement performants pour la synthèse de revêtements à propriétés contrôlées. Plus spécifiquement, ce travail de recherche porte sur l'élaboration de revêtements biocompatibles, sur alliage titane TiAl6V4, obtenus par pulvérisation magnétron en conditions réactives. Dans un premier temps, nous avons décrit les procédés de mise en forme des implants commerciaux pour pouvoir les reproduire au niveau du laboratoire. Dans un second, nous avons focalisé notre étude sur l'effet de la structure cristallographique de films de zircone sur leur caractère biocompatible à partir de cultures cellulaires de fibroblastes. Les résultats ainsi obtenus démontrent très nettement des différences de comportement entre des films de zircone monoclinique, quadratique ou cubique. Dans l'objectif d'apporter des éléments d'information permettant de discuter de ces effets, d'autres séries de revêtements céramiques ont été élaborées comme par exemple des oxydes de titane ou de zirconium amorphes, de l'oxyde d'yttrium, de l'oxyde d'aluminium ou encore du carbone amorphe. Les cultures cellulaires pratiquées sur ces échantillons ont permis de démontrer le caractère biocompatible de l'oxyde d'yttrium excluant ainsi tout effet nocif de cet élément dans les zircones dopées / The vapor deposition processes are particularly successful for the synthesis of coatings with tuneable properties. More specifically, this research deals with the development of biocompatible coatings on titanium alloys TA6V obtained by magnetron sputtering in reactive conditions. At first, we described the processes to design the commercial medical implants to be able to reproduce them within the laboratory. In the second, we focused our study on the effect of the crystallographic structure of zirconia-based coatings on their biocompatible character from cell cultures of fibroblasts. The results obtained demonstrate a significant variation of cell behavior for the three the zirconia structures: monoclinic, tetragonal or cubic. In the purpose to bring relevant information that allow discussing these effects, another series of ceramic coatings were developed as for instance amorphous oxides of titanium or zirconium, yttrium oxide,, aluminum oxide or amorphous carbon. The cell response on these samples demonstrates to the biocompatible properties of the yttrium oxide, excluding any harmful effect of this element in the doped zirconia

Neste trabalho, apresento um estudo sobre a fabricação e caracterização físico-química de filmes finos de nitreto de alumínio (AlN) obtidos pela técnica de pulverização catódica reativa por rádio frequência (r.f sputtering) utilizando um alvo de alumínio puro. Visto que o AlN é um material que apresenta piezoeletricidade e compatibilidade com a tecnologia MOS, o objetivo principal desse trabalho é definir os parâmetros de processo de deposição que resultem em um material com propriedades adequadas para sua utilização como elemento atuador e/ou sensor em sistemas micro eletromecânicos (MEMS). O estudo da influência dos parâmetros de processo foi realizado em três etapas. Na primeira realizei um estudo preliminar sobre a influência da pressão de processo e potência de r.f. Na segunda etapa realizei um estudo sobre a influência da relação entre o gás reativo (N2) e o pulverizante (Ar) nas características físicoquímicas do material. Na 3º etapa estudei o efeito da temperatura de deposição nas características do filme que apresentou as propriedades mais propícias para aplicações em MEMS. Propriedades como índice de refração, composição química e stress residual não apresentaram grandes variações com a mudança da composição gasosa da atmosfera de deposição, no entanto, os resultados de difração de raios-X mostraram que os filmes obtidos com 30% de N2 possuem maior cristalização na direção que apresenta maior piezoeletricidade, sendo assim, mais favorável para ser utilizado como sensor/atuador na fabricação de MEMS. No estudo sobre o efeito da temperatura de deposição verificamos que o filme crescido a 250°C apresentou as melhores propriedades para as aplicações em MEMS desejadas. Para finalizar o trabalho a constante piezoelétrica de carga foi obtida utilizando capacitores de placas paralelas de molibdênio e o AlN como dielétrico, obtendo um coeficiente piezoelétrico de carga d33 de 0,5 pm/V. / I present a study on the production and physicochemical characterization of aluminum nitride thin films (AlN) obtained by r.f. reactive magnetron sputtering, using a target of pure aluminum. Since AlN is a material that presents piezoelectricity and compatibility with MOS technology, the main objective of this work is to define the process parameters that will result in a material with properties suitable for its use as an actuator / sensor in micro electromechanical systems (MEMS). The process parameters influence study was performed in three steps. First I conducted a preliminary study on pressure process and rf power influence. In the second step was studied the influence of the reactive (N2) and sputtering (Ar) gas ratio on the material physical and chemical properties. Last but not least, I studied the temperature deposition effects in the AlN thin film obtained in the gas ratio which presented the most favorable properties for MEMS applications. Properties such as refractive index, chemical composition and residual stress did not show considerable variations with changing in the atmosphere deposition, however X-ray diffraction results showed films obtained with 30% N2 have higher crystallization in (002) direction, which is the one with greater piezoelectricity response and thus, more favorable to be used as sensor / actuator in MEMS fabrication. The study on deposition temperature effects has shown maximum (002) crystallization direction is achieved in films grown at 250° C. Piezoelectric coefficient was defined using parallel plate capacitors method using AlN as dielectric resulted in a d33 piezoelectric coefficient of 0,5 pm/V.

Neste trabalho, apresento um estudo sobre a fabricação e caracterização físico-química de filmes finos de nitreto de alumínio (AlN) obtidos pela técnica de pulverização catódica reativa por rádio frequência (r.f sputtering) utilizando um alvo de alumínio puro. Visto que o AlN é um material que apresenta piezoeletricidade e compatibilidade com a tecnologia MOS, o objetivo principal desse trabalho é definir os parâmetros de processo de deposição que resultem em um material com propriedades adequadas para sua utilização como elemento atuador e/ou sensor em sistemas micro eletromecânicos (MEMS). O estudo da influência dos parâmetros de processo foi realizado em três etapas. Na primeira realizei um estudo preliminar sobre a influência da pressão de processo e potência de r.f. Na segunda etapa realizei um estudo sobre a influência da relação entre o gás reativo (N2) e o pulverizante (Ar) nas características físicoquímicas do material. Na 3º etapa estudei o efeito da temperatura de deposição nas características do filme que apresentou as propriedades mais propícias para aplicações em MEMS. Propriedades como índice de refração, composição química e stress residual não apresentaram grandes variações com a mudança da composição gasosa da atmosfera de deposição, no entanto, os resultados de difração de raios-X mostraram que os filmes obtidos com 30% de N2 possuem maior cristalização na direção que apresenta maior piezoeletricidade, sendo assim, mais favorável para ser utilizado como sensor/atuador na fabricação de MEMS. No estudo sobre o efeito da temperatura de deposição verificamos que o filme crescido a 250°C apresentou as melhores propriedades para as aplicações em MEMS desejadas. Para finalizar o trabalho a constante piezoelétrica de carga foi obtida utilizando capacitores de placas paralelas de molibdênio e o AlN como dielétrico, obtendo um coeficiente piezoelétrico de carga d33 de 0,5 pm/V. / I present a study on the production and physicochemical characterization of aluminum nitride thin films (AlN) obtained by r.f. reactive magnetron sputtering, using a target of pure aluminum. Since AlN is a material that presents piezoelectricity and compatibility with MOS technology, the main objective of this work is to define the process parameters that will result in a material with properties suitable for its use as an actuator / sensor in micro electromechanical systems (MEMS). The process parameters influence study was performed in three steps. First I conducted a preliminary study on pressure process and rf power influence. In the second step was studied the influence of the reactive (N2) and sputtering (Ar) gas ratio on the material physical and chemical properties. Last but not least, I studied the temperature deposition effects in the AlN thin film obtained in the gas ratio which presented the most favorable properties for MEMS applications. Properties such as refractive index, chemical composition and residual stress did not show considerable variations with changing in the atmosphere deposition, however X-ray diffraction results showed films obtained with 30% N2 have higher crystallization in (002) direction, which is the one with greater piezoelectricity response and thus, more favorable to be used as sensor / actuator in MEMS fabrication. The study on deposition temperature effects has shown maximum (002) crystallization direction is achieved in films grown at 250° C. Piezoelectric coefficient was defined using parallel plate capacitors method using AlN as dielectric resulted in a d33 piezoelectric coefficient of 0,5 pm/V.

<p>Electro-acoustic devices such as surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices have been in commercial use for over 60 years and can be found in applications ranging from specialised scientific and military equipment to consumer products, such as mobile telephones, TV and radio receivers, etc. Today by far the largest market for electro-acoustic devices is the telecommunication industry which annually consumes approximately three billion acoustic wave filters for frequency control alone.</p><p>The development of new materials and technologies for electro-acoustic devices has gained a substantial and growing interest from both academic and industrial research communities in recent years due to the enormous growth in the telecommunication industry and other forms of wireless data communication. One of the bigger issues has been to replace the single crystalline substrates with thin film piezoelectric materials deposited by reactive sputtering. This would not only reduce the manufacturing costs but will also enable high frequency of operation and a wider choice of substrate materials. However, in order to obtain the material properties required for the intended application a detailed theoretical description of the reactive sputtering process is necessary since the texture and other functional properties of the piezoelectric material are extremely sensitive to the process parameters in addition to the structure of the underlying material.</p><p>This thesis studies the reactive sputtering process and its application for the fabrication of thin film electro-acoustic devices. The aim has been to gain a further insight into the process and make use of this knowledge to improve the fabrication of electro-acoustic devices. In this work modelling of the reactive sputtering process has been improved by studying certain fundamental aspects of the process and in particular the dynamics of the processes taking place during sputtering both at the target and the substrate surfaces. Consequently, highly textured thin piezoelectric aluminium nitride films have been synthesized and thin film bulk acoustic resonators (FBAR) operating in the GHz range have been fabricated and studied.</p>

Le but de ce travail est d’étudier l’effet de la vapeur d’eau contenue dans le plasma sur la composition et la vitesse de dépôt des couches minces d’oxynitrures de chrome déposées par pulvérisation cathodique magnétron réactive avec l’air contenant différentes teneurs en vapeur d’eau (humidité relative). Les techniques d’analyses par faisceau d’ions énergétiques : RBS et réactions nucléaires nous ont permis de déterminer les concentrations relatives des éléments déposés. Les profils d’hydrogène et d’azote ont été déterminés par RNRA et Tof- SIMS. La liaison chimique a été identifiée par LEEIXS et XPS. Les mesures XPS ont dévoilé la présence d’une phase autre que Cr, CrN, Cr2O3 et CrO2 ; cette nouvelle phase possède une stoechiométrie (CrO2)3-N. La teneur en Cr et ses composés varie en fonction du flux et de l’humidité relative de l’air. En mode métallique de la pulvérisation cathodique, la stoechiométrie Cr2O3 est majoritaire en coexistence avec de faibles teneurs et CrN, CrO2 et (CrO2)3-N alors qu’en mode composé, c’est la stoechiométrie CrO2 qui prédomine./ The aim of this work is to study the stoichiometry of chromium oxynitride thin films deposited by reactive magnetron sputtering in presence of air with various relative humidities. Ion Beam Analysis methods: RBS (Rutherford Backscattering Spectroscopy) and resonant nuclear reaction (RNRA) were used to determine the thickness and the composition of the films. Hydrogen and nitrogen profiles were obtained by RNRA and Tof-SIMS. The chemical bonds were investigated by XPS and LEEIXS. The chromium metallic and chromium compounds concentrations were measured versus the flow and relative humidity of the air. During sputtering in metallic mode, Cr2O3 stoichiometry is observed with low contents of CrN, CrO2 and (CrO2)3-N whereas in compound mode the CrO2 stoichiometry predominates.

Electro-acoustic devices such as surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices have been in commercial use for over 60 years and can be found in applications ranging from specialised scientific and military equipment to consumer products, such as mobile telephones, TV and radio receivers, etc. Today by far the largest market for electro-acoustic devices is the telecommunication industry which annually consumes approximately three billion acoustic wave filters for frequency control alone. The development of new materials and technologies for electro-acoustic devices has gained a substantial and growing interest from both academic and industrial research communities in recent years due to the enormous growth in the telecommunication industry and other forms of wireless data communication. One of the bigger issues has been to replace the single crystalline substrates with thin film piezoelectric materials deposited by reactive sputtering. This would not only reduce the manufacturing costs but will also enable high frequency of operation and a wider choice of substrate materials. However, in order to obtain the material properties required for the intended application a detailed theoretical description of the reactive sputtering process is necessary since the texture and other functional properties of the piezoelectric material are extremely sensitive to the process parameters in addition to the structure of the underlying material. This thesis studies the reactive sputtering process and its application for the fabrication of thin film electro-acoustic devices. The aim has been to gain a further insight into the process and make use of this knowledge to improve the fabrication of electro-acoustic devices. In this work modelling of the reactive sputtering process has been improved by studying certain fundamental aspects of the process and in particular the dynamics of the processes taking place during sputtering both at the target and the substrate surfaces. Consequently, highly textured thin piezoelectric aluminium nitride films have been synthesized and thin film bulk acoustic resonators (FBAR) operating in the GHz range have been fabricated and studied.

CdTe solar cells in the superstrate configuration have achieved record efficiencies of 16% but those in the substrate configuration have reached efficiencies of only 7.8%. A major reason for the lower efficiency of substrate CdTe solar cells is the poor back contact. In this work, CdTe solar cells of the substrate configuration have been fabricated on flexible metallic substrates. For this type of devices, impurity diffusion out of stainless-steel substrates due to high temperature processing can be a cause for poor cell performance. It is necessary to investigate ways of improving the back contact by trying to mitigate the above factors. In this work, Nitrogen has been incorporated in Molybdenum by RF magnetron sputtering. Nitrogen incorporation has helped achieve a 2% increase in efficiency for the best cell and an improvement of 1.5% on an average.

Thin film technology is of great significance for a variety of products, such as electronics, anti-reflective or hard coatings, sensors, solar cells, etc. This thesis concerns the synthesis of thin functional films, reactive magnetron sputter deposition process as such and the physical and functional characterization of the thin films synthesized. Characteristic for reactive sputtering processes is the hysteresis due to the target poisoning. One particular finding in this work is the elimination of the hysteresis by means of a mixed nitrogen/oxygen processing environment for dual sputtering of Alumina-Zirconia thin films. For a constant moderate flow of nitrogen, the hysteresis could be eliminated without significant incorporation of nitrogen in the films. It is concluded that optimum processing conditions for films of a desired composition can readily be estimated by modeling. The work on reactively sputtered SiO2–TiO2 thin films provides guidelines as to the choice of process parameters in view of the application in mind, by demonstrating that it is possible to tune the refractive index by using single composite Six/TiO2 targets with the right composition and operating in a suitable oxygen flow range. The influence of the target composition on the sputter yield is studied for reactively sputtered titanium oxide films. It is shown that by using sub-stoichiometric targets with the right composition and operating in the proper oxygen flow range, it is possible to increase the sputter rate and still obtain stoichiometric coatings. Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Within this thesis (Al,B)N films of the wurtzite structure and a strong c-axis texture have been grown by reactive sputter deposition. Nanoindentation experiments show that the films have nanoindentation hardness in excess of 30 GPa, which is as hard as commercially available hard coatings such as TiN. Electrical properties of w-(Al,B)N thin films were investigated. W-(Al,B)N thin films are found to have a dielectric strength of ~3×106 V/cm, a relatively high k-value around 12 and conduction mechanisms similar to those of AlN. These results serve as basis for further research and applications of w-(Al,B)N thin films. An AlN thin film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR) together with a microfluidic transport system have been fabricated. The fabrication process is IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. The results on IC-compatibility, Q-values, operation frequency and resolution illustrate the potential of this technology for highly sensitive low-cost micro-biosensor systems for applications in, e.g. point-of-care testing.

Submitted by Nilton Francelosi Azevedo Neto (nilton@fc.unesp.br) on 2018-11-22T13:54:33Z No. of bitstreams: 1 Azevedo Neto- Tese POSMAT-2018.pdf: 3312025 bytes, checksum: 69a53514543bbe65b47c2fd62ddb6168 (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-11-22T16:48:03Z (GMT) No. of bitstreams: 1 azevedoneto_nf_dr_bauru.pdf: 3312025 bytes, checksum: 69a53514543bbe65b47c2fd62ddb6168 (MD5) / Made available in DSpace on 2018-11-22T16:48:03Z (GMT). No. of bitstreams: 1 azevedoneto_nf_dr_bauru.pdf: 3312025 bytes, checksum: 69a53514543bbe65b47c2fd62ddb6168 (MD5) Previous issue date: 2018-09-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A motivação para este trabalho foi buscar uma melhor compreensão sobre o processo de crescimento dos filmes de óxido de cobalto pela técnica de DC magnetron sputtering reativo. Os filmes de interesse foram depositados sobre substratos de sílica amorfa (a -SiO2 ), aluminato de lantânio (LaAlO3 ) e safira - c (Al2O3- c) usando diferentes valores de potência de deposição e fluxo de oxigênio . As condições de crescimento dos filmes foram analisadas utilizando simulação computacional do processo de sputtering reativo baseada no modelo de Depla, medidas da emissão óptica das espécies presentes no plasma e monitor amento da taxa de crescimento através de uma microbalança de quartzo. Os resultados de difração de raios X mostraram que em baixa potência é obtida a fase Co3O4 espinélio, enquanto que em alta potência os filmes apresentaram a fase CoO cúbica . A s simulações computacionais do processo de sputtering reativo indicaram que , quando as potências de deposição são baixas, o processo de crescimento dos filmes ocorre com o alvo no regime “envenenado” . Em contraste, altas potencias favorece m o regime metálico do alvo. Medidas de emissão do plasma de deposição mostraram que em baixa potência de deposição a intensidade da linha de emissão do oxigênio é alta , porém com o aumento da potência sua intensidade diminui e a d a linha do cobalto aumenta. O s filmes de Co 3 O 4 depositados sobre substratos cristalinos apresentaram resultados promissores . Medidas de difração de raios X de alta resolução , utilizando radiação síncrotron , indicaram que a deposição do Co 3 O 4 sobre Al2O3 - c resultou em crescimento epitaxial na qual a direção [ 111] do cristal de Co 3 O 4 é perpendicular à superfície do substrato de safira - c (0001). Enquanto que a deposição sobre LaAlO 3 resultou em crescimento com forte textura de orientação, com as direções [220] e [400] perpendiculares à superfície dos substratos . Os espectros Raman dessas amostras apresentaram picos de vibração bem definidos e característicos da fase Co 3 O 4 e a análise do Raman polarizado do s filmes de Co 3 O 4 sobre Al 2 O 3 - c concorda m com as regras de seleção para a orientação [111] . Para os filmes c om fase Co 3 O 4 , medidas de transmitância na região do UV - Vis - NIR mostraram alta absorção na região do visível e bandas de absorção no infravermelho próximo relacionadas a transições eletrônicas dos íons de Co 2+ e Co 3+ . Para esse crescimento observou - se também resposta intensa de fotocondutividade com exc itação em 405 nm e 532 nm em 10 K. Testes preliminares de fotocatálise indicaram que os filmes de Co 3 O 4 produzidos possuem uma pequena atividade fotocatalítica para degradação do corante Rodamina B. Neste trabalho uma correlação direta entre as condições de crescimento e as mudança s de fase do s filmes foi obtida, demonstrando a versatilidade da técnica de sputtering para crescimento de filmes de óxido de cobalto para estudos científicos e aplicações tecnológicas. / The motivation for this work was to obtain a better understanding of the growth process of cobalt oxides by the DC magnetron reactive sputtering technique. The films were dep osited on amorphous silica (a-SiO2), lanthanum aluminate (LaAlO3) and sapphire-c (c-Al2O3) substrates using different values of deposition power and oxygen flow. The conditions of growth of the films were analyzed using the optical analysis of the species present in the plasma and the monitoring of the growth rate through a quartz microbalance. The X-ray diffraction results showed that at lower powers the Co3O4 phase was obtained, while at high er power s the films presented the CoO cubic phase. The computational simulations of the reactive sputtering process indicated that, at low deposition power, the gro wth process of the films occurs with the target in the "poisoned" regime, while in high powers it favors the metallic regime of the target. Plasma emission measurements showed that at low deposition power the oxygen intensity is high while at high power it s intensity decreases and that of cobalt increases. The Co 3 O 4 films deposited on crystalline substrates showed promising results. High - resolution X-ray diffraction measurements using synchrotron radiation indicated that the deposition of Co3O4 on c-Al2O3 resulted in epitaxial growth , in which the direction [111] is perpendicular to the surface of the c - sapphire (0001) substrates. However, the deposition on LaAlO 3 resulted in growth with strong texture in the directions [220] and [400]. The Raman spectra of these samples showed well - defined vibration peaks characteristic of the Co3O4 phase . The polarized Raman analysis of Co 3 O 4 deposited on c-Al2O3 agrees with the selection rules for the [111] orientation, in agreement with the high resolution X-ray diffraction analysis . In the optical transmittance measurements , t he films with Co 3 O 4 phase displayed high absorption bands in the region of the visible and near - infrared . These bands are related to el ectronic transitions of the Co2+ and Co3+ ions. For these films , strong photoconductivity responses were observed for excitations at 405 nm and 532 nm at 10 K . Preliminary photocatalysis tests indicated that the Co3O4 films produced by sputtering have a small photocatalytic activity for Rhodamine B (RhB) dye degradation. Concluding , a direct correlation between the growth conditions and the phase changes of the films was obtained, demonstrating the versatility of the sputtering technique for the growth of cobalt oxide films for scientific studies and technological applications.