P06

Fabrication of nano-structure for Sb2Te3
Hideaki Uratsuji1, Masashi Kuwahara2, Yoichi Uehara3, Joe Sakai4, Sumio Hosaka5
1Shibaura Eletec Co., 2AIST., 3 Tohoku Univ., 4 Tours Univ., 5 Gunma Univ.
1
Yokohama Kanagawa Japan, 2Tsukuba Ibaraki Japan, 3Sendai Miyagi Japan, 4 Tours France, 5Kiryu Gunma Japan
Key words: Phase Change materials, Sb2Te3, Nano-structures
1. INTRODUCTION
We have studied nano-structure of chalcogenide [1] because we are interested in physical property of chalcogenide
nano-structure for applying them to memory devices. In this paper, we report nano-structure shape of Sb2Te3
fabricated by various annealing conditions. A scanning electron microscope (SEM) and an atomic force microscope(AFM) were used for observing shapes.
2. EXPERIMENTS
Nano-structure is fabricated by annealing after sputtering Sb2Te3 with the thickness of 5 nm on Highly Oriented
Pyrolytic Graphite (HOPG). HOPG was used as substrate because its surface flatness is atomic level and it is easy torecognize nano-structure on it. Sputtering conditions are described below; Ar gas flow rate:10 sccm, gas pressure: 0.7
Pa, and RF magnetron power:50 W. After the deposition, we carried out annealing process at 200 or 250 ℃ with theannealing speed of 10 ℃/ min. And we kept its temperature for 5 min. Shape observation of nano-structure wascarried out by SEM and AFM.
3. RESULTS AND DISCUSSION
Fig. 1 is an SEM image after annealing Sb2Te3 film at 200 ℃ for 5 min. It is clearly seen that nano-particles with 5
to 25 nm diameter are generated. We analyzed the distribution of the diameter, and 65% Sb2Te3 has the diameterwithin 5 to 15 nm and the 35% has the diameter within 15 to 25 nm. Fig. 2 is an SEM image after annealing at 250 ℃
for 5 min. Nano-needle structure with the length of several tens hundreds nm and the width of 50 nm were produced.
These needles are not only lying but also standing on the substrate surface. We annealed Sb2Te3 thin film at 200 ℃
for 60 min, nano-needle structures were also generated shown in Fig. 3. We carried out AFM observation to obtainstructure information of the needle. Fig. 4 is an AFM image of the nano-needle structure. Flat portion was observed on
this AFM images, therefore, we think that the nano-needle structure have possibly quadratic shape.

Fig. 1 SEM image of nano-particles after
annealing at 200 ℃ for 5 min.

Fig. 2 SEM image of nano-needle structures after
annealing at 250 ℃ for 5 min.

Fig. 3 SEM image of nano-needle structures after
annealing at 200 ℃ for 60 min

48.88
(nm)

A-B

AB

0.00

0.00

←34.06→

138.68 (nm)Fig. 4 AFM image of top（left）and cross-sectional view（right） of the nano-needle structure. Flat portion was clearlyseen.
4. CONCLUSION
We carried out fabrication of Sb2Te3 nano-structure by annealing, and studied the shape depending on annealing
temperature and time by SEM and AFM. Nano-particle structures were produced at 200 ℃ for 5min, on the other
hand, nano-needle structure appeared on substrate at 250 ℃ for 5min and 200 ℃ for 60 min. From AFM observation,
the nano-needle structure would have quadratic shape. In the future works, we will plan to measure electric and opticalproperties to individual nano-structure using SPM and TEM.
ACKOWLEADGMENT

We appreciate M. Nakazato and W. yang in Shibaura Eletec Co. for supporting this work and discussion.
REFERENCES[1] H.R. Yoon et al. / Journal of Non-Crystalline Solids 352 (2006)