Optical And Electrical Properties Of Mn-Co-Ni-O Thin Films Prepared By Radio Frequency Magnetron Sputtering

Mn-Co-Ni-O transition metal oxides with the spinel structure of general formula AB2O4, are wildly used in thermal sensors and infrared detection. This material exhibits various excellent performances with higher temperature coefficient of resistance(TCR), excellent aging resistance performance, wide operating temperature range, broad band optical response and long stability in operation. The Mn-Co-Ni-O materials are always prepared by physical methods and chemistry methods. The method such as high temperature solid-phase synthesis has mature technology process system. In this paper, based on high temperature solid-phase synthesis method, Mn-Co-Ni-O thin films with different thickness are fabricated on thermally oxidized Si(100) substrate by radio frequency magnetron sputtering method. Microstructure, electrical properties as well as optical properties of the Mn-Co-Ni-O films dependence of thickness are investigated in detail. This paper mainly relies on normative study and describes from several following aspects:(1) The investigation of production practice to prepare Mn-Co-Ni-O films by radio frequency magnetron sputtering methodMn-Co-Ni-O thin films are fabricated on Si Ox /Si substrate by radio frequency magnetron sputtering method. By comparing a series of experimental results and data, the optimal growth conditions for the growth of Mn-Co-Ni-O films are obtained. Finally, we wish to change the growth conditions to control the thickness of Mn-Co-Ni-O films. This can provide references for the miniaturization of Mn-Co-Ni-O ceramic materials.(2) The structure, morphology of Mn-Co-Ni-O thin filmsMn-Co-Ni-O thin films with different thickness are prepared by radio frequency magnetron sputtering method. Quantitative and qualitative analysis of the structure, surface morphology and ion distribution properties are measured by EDS, XRD, FESEM, AFM and XPS. The XPS results showed that there is no significant difference between element distributions in Mn-Co-Ni-O films with different thickness, but there is a tendency that the percentages of Mn3+ /Mn4+decrease firstly until the thickness reach to 693 nm, and then increase when the thickness surpass 693 nm.(3) The electrical properties of Mn-Co-Ni-O thin filmsPrevious research shows that with the film thickness(d) increasing, the room temperature resistance(R0) and the characteristic temperature(T0) all decrease. In accordance with this tendency, bulk material should have the lower characteristic temperature than film material,but this is not true in our research. In general, there is no significant difference between bulk and film material in T0. Interestingly, the characteristic temperature, as a function of thickness(200nm-900nm), is investigated in this study, the experimental evidence showed a liner relation between 1/T0 and(d-dc)2 or ln(T0) and(d-dc)2(dc, the transformation thickness of T0). In order to ensure the accuracy of curve fitting, other researchers’ experimental results are studied and their experimental data agree to fitted data well. To explain this phenomenon, this study combined with Hall testing and small polaron hopping model is carried out.(4) The optical properties of Mn-Co-Ni-O thin filmsThe optical proprieties of Mn-Co-Ni-O thin films with different thickness have been investigated by infrared spectroscopic ellipsometry. By fitting the measured ellipsometric data, the refractive index and extinction coefficient of Mn-Co-Ni-O films with different thickness in near infrared and visible region are performed.