JPS5937604A - How to create superionically conductive thin films - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides β-
AI! 203. β-Ga203. Na5Zr2Si2P
The present invention relates to a manufacturing method for forming a thin film such as O02°Ls 14Zrl (Ge04)4 by sputtering.

In recent years, interest in superionically conductive materials has been increasing. In particular, alkali ion conductors are attracting attention as solid electrolytes for Na-8 batteries and T and I batteries. The former is being put into practical use as automobile batteries and storage batteries for load leveling. In addition, the latter is rapidly becoming more widely used in recent years, as there has been an increasing demand for thinner batteries as electronic devices become smaller and thinner. There have also been attempts to solidify electrochromic displays using the above-mentioned solid LM materials, and the emergence of stable solid electrolytes with high ionic conductivity is strongly desired.

One possible method for increasing the ionic conductivity of the device is to reduce the resistance geometrically by making the solid electrolyte thinner. However, with conventional ceramic technology, the film thickness is 10
It is difficult to create a thin film of μm or less. Further, even if conventional film forming techniques such as the CVI method and the sputtering method were used, a thin film with high ionic conductivity could not be obtained. This is because (1) the synthesis temperature of the solid electrolyte is high, and (2) the alkali metal oxide is lost due to evaporation during thin film formation, making it difficult to control the composition. Things like that. Furthermore, since the crystallinity of the film obtained by film formation at normal low temperatures is poor, a thin film with good ion conductivity has not been obtained. The present invention has been made to eliminate these drawbacks of the prior art and to create a thin film with excellent ion conductivity. In addition, as a sputtering target, the superionic conductive compound and L
iA702゜LiGaO2, Li2CO3, NaAt!
02. A powder mixed with an alkali compound such as NaGaO2°N a 2 C03 is used. The reason for using powder is that ■ the alkali concentration in the thin film can be freely controlled; ■
Since NaM02 (M=A/', Ga) and the like are deliquescent, it is difficult to make a mixed sintered target.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1゜Ga2O3 and Na2CO3 raw material powders were mixed in a scale at a molar ratio of 4:l, and reacted at 1100°C for 10 hours to produce Na
-β"-G a 203 is created. Also, the 1 molar ratio is adjusted and NaGaO2 powder is created in the same manner. These powders are converted into Na2.G44Ga203: NaGa
They were mixed so that O2 == 1:2- (mol), and this powder was used as a target to form a thin film using a sputter-up method. Further, in this example, a planar magnetron high speed sputtering method was adopted. Using the above target, substrate temperature: 300'O, degree of vacuum = 2x
10-2mm Hg, discharge gas: (Ar 102=
The film was created under sputtering conditions of 60/40) and film formation rate: 0.4 μm/1H. A film with a thickness of 2/1 m was created on a SiO□ and alumina substrate, and the ionic conductivity was measured.
cm-'. Note that when a target consisting only of β〃G a 203 powder is used, the ionic conductivity of the film prepared under the same conditions as above is 4 × 10−7 × 5−
cm-'. This is due to the alkali being lost by evaporation during sputtering, and it can be seen that it is very important to control the target solar cell formation as desired.

Example 2゜MgAe204 or alumina is used as a substrate, Example 1
Under the same sputtering conditions, a 1.5 μm thick N
An a-βGa2O3 thin film was created. Furthermore, this thin film was heat-treated at a temperature of 600°C to 1000"O for 3 hours each to improve crystallinity and ionic conductivity.
The figure shows the temperature change (Arrhenius plot) of the ionic conductivity measured in the direction parallel to the substrate surface of the Na-βGa2O3 thin film after heat treatment. In Figure 1, 1 shows the sample as sputtered, and 2 and 3.4 show the ionic conductivity after heat treatment at 600°C and 1000°C, respectively. The activation energies for conduction are shown in Table 1 along with the values for single crystals.

Table 1 Heat treatment temperature Activation energy ('O) (Kca/'/mo/?) Untreated 17 600 13 007 1000 5 Single crystal 4 The thin film heat-treated with It can be seen that the activation energy is almost equal to that of a single crystal, which is just one order of magnitude smaller than that of a crystal, and the film has extremely good properties.

In the case of Na-βAl2O3, the target composition is also changed to Na2
O・11 Al 203: NaAj? 02 == 1
: 2 (rnoe), β-Ga203
A thin film was obtained that showed almost the same ionic conductivity as .

Example 3゜Na2CO3, ZrO2, NH4H2PO4, 5I02
The raw material powders are mixed on a scale to have a composition of Na5Zr2Si2PO□2, and Na5Zr2Si2PO is formed by solid phase reaction.
,. A powder was created.

Furthermore, NaCO3 was added to this powder to add Na5Zr2SI2P.
O12: NaCO3= 1 : 3 (mo/')
``Three matches made the target a good success.''

A thin film with a thickness of 5 μm was created under the same sputter link conditions as in Example 1, and then heat-treated in SOOA. The ionic conductivity of the thin film thus obtained was 2 x 10-<7-cm-' at 2000.

As explained above, according to the present invention, an R film with extremely high ionic conductivity can be obtained even in a thin film of 51 zm or less. Since the thickness of the thin film 1 is three orders of magnitude smaller than that of the bulk material, the ionic conduction is three orders of magnitude greater, and this can be expected to have a significant effect when the solid electrolyte is applied to various devices.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an Arrhenius plot of ion conduction in a superionically conductive thin film produced by the method of the present invention. 1... In the case of a sample that has been sputtered, 2...
・When heat treated at 6oo'C, 3...When heat treated at 900°C, 4...When heat treated at 900°C.

Claims (1)

[Claims] 1. A superionically conductive thin film characterized in that it is deposited on a substrate by sputtering using a powder mixture of a superionically conductive compound and an alkali metal compound as a target. How to make. 2. Using a powder mixture of a superionically conductive compound and an alkali metal compound as a target, deposit a superionically conductive thin film on a substrate by sputtering, and then heat treat the thin film at 600-1000υ. A method for producing a superionically conductive thin film characterized by the following.