Development of plasma synthesis technology for advanced complex compound materials based on mass-selective momentum control

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We have developed the experimental apparatus of new plasma processing oriented to the advanced functional oxide compounds such as ZnO film, applying the mass-selective momentum control based on the ponderomotive force on the magnetized ions. The ponderomotive potential generated by the localized rf electric field with the frequency ω is superimposed on the collision-less sheath of the sample substrate. Then the composition and crystal orientation of ZnO are expected to be controlled just before the substrate by varying ω near the cyclotron frequency Ω_o (or Ω_<zn>) and Ω_o (orΩ_<zn>)-ω, respectively. Although the oxide dominates the carrier concentration and is very sensitive for process pressure and temperature, this new way could draw more the theoretical properties of the oxide compounds than the conventional sputtering type.The flux depression of oxygen ion upon the substrate has been demonstrated accompanying with the ponderomotive effect on the magnetized reactive molecular ion. … More This phenomenon connecting to mass-selective momentum control is applied to synthesis the ZnO transparent conductive film with lower resistivity comparable to the Indium based film. The enhancement of ponderomotive force, being necessary for high selectivity of cyclotron ion's species, is expected to appear by decelerating ion's initial velocity proportional to the square root of electron temperature in a plasma. To confirm this expectation even in a plasma, we have prepared the low-temperature plasma extracted from ECR oxygen plasma around a pressure of 10^<-2> Pa and investigated the enhancement effect of the ponderomotive force against electron temperature.The mixture plasma source is developed by evaporating zinc into ECR oxygen plasma confined by the axial magnetic field. The O^+, O_2^+, and Zn^+ exist in our plasma at a low pressure of 10^<-2> Pa when oven temperature exceeds around 400℃. The vapor source can move 3-dimensionally, searching the more proper deposition geometry with in-situ mass-spectroscopy and/or film thickness measurement. The resistivity measurement of ZnO transparent conductive film has been performed during the deposition.It is found that the resistivity of film with 〜 100 nm thickness decreases until 〜 10^<-4>Ωcm when ω approaches to the cyclotron frequency for the singly charged oxygen molecular. This phenomenon is considered to be attributed to the reflection of the oxygen molecular ion due to the ponderomotive force. Less