Chemical Nanoparticle Deposition of Oxide Nanostructured Thin Films
Y.-J. Chang, Y.-W. Su, D.-H. Lee, C.-H. Chang
Department of Chemical Engineering, Oregon State University,
Corvallis, OR 97331, USA
S.-Y. Han, J.-Y. Jung, N.-K. Park, T.-J. Lee, S.-O. Ryu
School of Chemical Engineering and Technology, Yeungnam University,
Kyongsan, 712-749, Korea
1. Abstract
2. Experimental Setup
200 nm
3. Characterization
We have developed a novel approach to deposit oxide
nanostructured thin films via a simple solution chemistry. This
approach uses a continuous-flow microreactor to continuously
generate a flux of nanoparticles which then impinge on a heated
substrate surface. The thin film formation follows a simple particle
s t i c k i n g m e c h a n i s m . F o r e x a m p l e , h i gh l y t r a n s p a r e n t
nanocrystalline ZnO thin films and exhibit a larger optical bandgap
at 4.35 eV were deposited using this technique. Functional ZnO
MISFETs were successfully fabricated using this technique after a
post air annealing process. In addition to ZnO, we have also
deposited, Fe3O4 and ZnxFe3-xO4 nanostructured thin films using this
approach. This new approach is promising as a low-cost deposition
technique for fabricating nanostructured thin films.
200 nm
Fig. 1-(a)
Fig.1-(b)
Fig.2-(b)
Fig.2-(a)
Fig.2-(c)
Fig.2-(d)
Fig.1. (a) TEM micrographs of the ZnO nanoparticles
(b) Electron diffraction pattern
Fig.2. (a) Top view SEM images of the annealed ZnO thin film
(b) Cross-sectional SEM images of the annealed ZnO thin film
(c) XRD pattern of the annealed ZnO thin film
(d) EDS analysis of the annealed ZnO thin film
Fig.3. (a) TEM micrographs of the ZnFe2O4 nanoparticles
(b) Electron diffraction pattern
Fig.3-(a)
Fig.3-(b)
200 nm
Effect of impinging time
Fig.4-(a)
Effect of temperature
Fig.4-(b)
Fig.4. SEM images of flower-like ZnO structures synthesized at 90℃
(0.1M NaOH); (a) for 1minute, (b) for 10minutes.
4. Bandgap estimation
Fig.5-(a)
Effect of concentration
Fig.5-(b)
Fig.6-(a)
Fig.5-(c)
Al
Al
Zinc Oxide
SiO2
p+ Silicon (Gate)
Au
300 nm
24 nm
6. Conclusions
100 nm
675 mm
500 nm
Fig.8-(a)
Fig.8-(c)
Fig.7-(a)
1.E-04
Ids (A)
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
-10
0
10
20
Vgs (V)
Fig.8-(b)
Fig.7-(b)
Fig.6-(d)
Fig. 7. (a) As-deposited, Eg = 4.35eV, (b) Annealed, Eg = 3.26eV
Fig. 8. (a) Structure of Metal Insulator Semiconductor Field Effect Transistor (MISFET)
(b) Drain current-drain voltage (Ids-Vds) output characteristics with Vgs = -10 ~ 40V
(c) Drain current-gate voltage (Ids-Vgs) at Vds = 1V showing a linear extrapolation method for threshold estimation
(d) Log (Ids)–Vgs transfer characteristics at Vds = 40 V.
5. Device characterization
Drain
Fig.6-(c)
Fig. 6. SEM images of flower-like ZnO structures synthesized with five different concentrations of NaOH at 90 ℃ for 5 minutes
(a) 0.005M, (b) 0.01M, (c) 0.05M, (d) 0.1M, (e) 0.15M
Fig.5. SEM images of flower-like ZnO structures synthesized at three different water bath temperatures
(0.1M NaOH, 5 minutes for impinging) (a) 60 ℃, (b) 80 ℃, (c) 90 ℃.
Source
Fig.6-(b)
Fig.8-(d)
30
40
The newly developed chemical nanoparticle deposition process was successfully used to
deposit ZnO thin films at low temperature (~80ºC). The flower-like ZnO structured
were observed by SEM. Three experimental parameters, impinging time, solution
temperature, and NaOH concentration play important roles in the growth of ZnO structure.
Other oxide nanoprticles, zinc ferrite (ZnFe2O4) also can be synthesized by this
impinging method. The bandgap estimation of annealed ZnO thin film is 3.26 eV which is
consistent with theoretical value. Functional ZnO MISFETs were fabricated by this
experimental setup after a post air-anneal process at 600˚C for 30 min. An effective
mobility, eff 0.16 cm2/V-s, a threshold voltage of 15 V, turn-on voltage of -4 V, and
current on-to-off ratio of ~104 are obtained from the MISFET. This deposition method
uses relatively simple chemistry and is capable of depositing nanostructured thin films
with high utilization of the reactants.
(201)
Fig.6-(e)