Electrical Properties of Novel Anodic Films Formed in Nonaqueous Electrolyte Solutions
- PDF / 225,254 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 92 Downloads / 195 Views
113
Mat. Res. Soc. Symp. Proc. Vol. 500 ©1998 Materials Research Society
Film formation Sputtered aluminum alloy films were anodized by a dc power source (Keithley, 2400 Digital SourceMeter). Anodization was carried out at a constant current (current density: 0.1 mA cm 2 ) up to 100 V, followed by a constant voltage (voltage: 100 V) for 120 min. Electrolyte solutions used are listed in Table 1. After anodization, these films were annealed at 350 'C in a nitrogen atmosphere for 1 hr using a clean oven (Koyo Lindberg, INH-9CD). Table 1. Electrolyte solutions Solvent
Solute
Propylene Carbonate (PC)
0.4 mol dm 3 Triethylmethylammonium Salicylate 0.4 mol dmi3 Triethylmethylammonium Salicylate
1.0
5.8
1.0
1.1
0.4 mol dmi3 Triethylmethylammonium Salicylate 0.4 mol dm 3 Triethylmethylammonium Salicylate
1.0
7.2
Ethylene Glycol (EG) y-Butyrolactone (GBL) Water (W)
Water Content
Electrolytic Conductivity
/ wt.%
/ mS cm'
12.0
E1.rctricrn MPq.-JrPimntSf
Aluminum for counter electrodes was deposited onto the annealed films by sputtering. Photolithography was used to forman array of dots lmm in diameter and 400 nm thick. The electrical contact to the MIM elements was established through pressure probes (Signatone, H100). Using a source-measure unit (Keithley, 237), a stair wave form voltage was applied from 0 V to 25 V with 1 V step and 1 s delay after each measurement. Surface Analysis Annealed films were characterized by scanning electron microscopy (SEM; Hitachi, S-900), transmission electron microscopy (TEM; Hitachi, H-600), and auger electron spectroscopy (AES; JEOL, JAMP-7800).
114
RESULTS AND DISCUSSION Anodization behavior A typical anodization curve is shown in Fig. 1. During the constant current process, voltage rises linearly to 100 V and current decreases rapidly in the constant voltage process. Q, and Q, are the electric charges used in constant current and constant voltage process, respectively. Residual current is measured at the end of the anodization process, and t,, is the time of the constant current process. 120 0.10 100 Qcc
0.08
80 in PC solution
0.06
60
S
0.04
40
0.02
20 IC
S.
1)
.
0
.
.
i
.
2000
.
.
.
.
.
4000
.
.
6000
.00
.
10( )00
8000
t/s ýA
Constant current process 2 (0.1 mA cm- , to 100 V)
Residual current
Constant voltage process (100 V, 120 min)
Fig. 1. Anodization behavior in propylene carbonate solution
Table 2.
Solvent
Comparison in anodization behavior
t.,
Q1.
/ min
/ C cm 2
/ C cmi2
Q,,,
Residual
Q + Q." %
Current /pA cm"2
PC
43
0.26
0.05
84
2.2
EG
49
0.29
0.06
83
2.8
GBL
46
0.27
0.09
75
2.3
Water
120
0.72
0.34
68
39.6
115
Comparison in anodization among nonaqueous solutions and an aqueous solution is shown in Table 2. Anodization behavior in the nonaqueous solutions was different from that in the aqueous solution. In nonaqueous solutions, anodization speeds were faster and the ratios of Q,, to Q, + Q., were higher. Low residual current can indicate high electrical resistance of the films. Current
Data Loading...
