Growth mechanism of YMnO3 film as a new candidate for nonvolatile memory devices

Abstract

We have proposed ReMnO3 (Re: rare earth) thin films for nonvolatile memory devices. We examine the growth mechanism of YMnO3 films on (0001)ZnO:Al/(0001) sapphire substrate using rf magnetron sputtering and pulsed laser deposition methods with oxide compound target. We have succeeded in obtaining (0001) epitaxial YMnO3 films on (111) MgO and (0001)ZnO:Al/(0001) sapphire substrate, and polycrystalline films on (111)Pt/(111)MgO. For an optimal structure, the film needed much less oxygen from the gas phase compared to other oxide films. The composition (Y/Mn ratio) of the YMnO3 films changed drastically by varying the partial oxygen pressure in the sputtering gas. In addition the Y/Mn ratio slinfled with sputter time due to target surface modification, probably caused by Y segregation. An extremely small amount of oxygen is required to form the YMnO3 crystal. This was confirmed by pulsed laser deposition experiments.

Electronic and crystal structure changes induced by in-plane oxygen vacancies in multiferroicYMnO3

“…The EELS spectra acquired from these two regions are shown as red and black lines in Fig. 2 [19]. Hence, the oxidizing ability of Y is much larger than that of Mn, which is in consistence with our experimental results.…”

Growth, optical and magnetic behavior of YMn0.35In0.65O3 thin film

“…It is also known from the literature that the substrate temperature can be reduced to 700 • C by using a buffer layer to obtain the hexagonal structure. 9 Here we report the growth, optical and magnetic studies on the YMn 0. 4 The Y(In,Mn)O 3 thin film was grown on c -plane Al 2 O 3 (0001) substrates (CrysTec, Germany) at 800 • C with an oxygen pressure of 20 mTorr by a pulsed laser deposition technique using KrF excimer laser (λ = 248 nm, 3 Hz).…”

Low leakage current characteristics of YMnO3 on Si(111) using an ultrathin buffer layer of silicon oxynitride

“…This temperature dependence of the growth manner is very similar to previous study using poor-crystalline surface as a buffer layer 21 and is characteristically different from the other ones using crystalline surfaces. 11,22 Repeated fabrications have clarified that the available temperature for ͑0004͒-oriented growth is limited in a narrow window ranging from 860 to 880°C. Concerning the ͑1121͒-oriented growth, on the other hand, temperature dependence is less critical.…”

“…This dependence on O 2 partial pressure seems to be more critical than that on other ordered surfaces. 11 Figures 7͑a͒ and 7͑b͒ represent the AFM images of the ͑0004͒-oriented and ͑1121͒-oriented YMO films, respectively. Both of the AFM images commonly show that average roughnesses of the surfaces about 10 nm, and that both of the surfaces consist of grains.…”

“…9,10 Not only growth mechanisms of YMO thin films but also the electric characteristics have been investigated so far. 11,12 Most of the studies are those in which well ordered surfaces are used as substrates.…”