Atmospheric Pressure Plasma Deposition of TiO2: A Review.

Atmospheric pressure plasma (APP) deposition techniques are useful today because of their simplicity and their time and cost savings, particularly for growth of oxide films. Among the oxide materials, titanium dioxide (TiO2) has a wide range of applications in electronics, solar cells, and photocatalysis, which has made it an extremely popular research topic for decades. Here, we provide an overview of non-thermal APP deposition techniques for TiO2 thin film, some historical background, and some very recent findings and developments. First, we define non-thermal plasma, and then we describe the advantages of APP deposition. In addition, we explain the importance of TiO2 and then describe briefly the three deposition techniques used to date. We also compare the structural, electronic, and optical properties of TiO2 films deposited by different APP methods. Lastly, we examine the status of current research related to the effects of such deposition parameters as plasma power, feed gas, bias voltage, gas flow rate, and substrate temperature on the deposition rate, crystal phase, and other film properties. The examples given cover the most common APP deposition techniques for TiO2 growth to understand their advantages for specific applications. In addition, we discuss the important challenges that APP deposition is facing in this rapidly growing field.

Total yield of reactive species originating from an atmospheric pressure plasma jet in real time.

It is now well established that plasma-induced reactive species are key agents involved in many biochemical reactions. This work reports on the formation of plasma reactive species in an acidified ferrous sulfate (Fricke) solution interacting with an atmospheric pressure plasma jet (APPJ). A yield of ferric (Fe3+) ions measured using in situ absorption spectroscopy was attributed to the formation of plasma reactive species provided and/or originated in the solution. The results indicated that the number of reactive species formed was proportional to plasma frequency and voltage. However, the Fe3+ yield per pulse decreased with increased frequency. To obtain a better understanding of the processes and species involved in the chemical reactions due to plasma exposure, Fe3+ yields were calculated and compared to the experimental data. At higher frequencies, there was insufficient time to complete all the reactions before the next pulse reached the solution; at lower frequencies, the Fe3+ yield was higher because of the relatively longer time available for reactions to occur. In addition, the comparison between DNA damage levels and Fe3+ yields was investigated under different experimental conditions in order to verify the usefulness of both the Fricke solution and the DNA molecule as a probe to characterize APPJs.