水热合成法制备HfO_2薄膜_英文_

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HfO2 Thin Films Prepared by
Hydrothermal Synthesis
Shen Jun, Wang Shengzhao, Wang Xiaodong, Zhang Zhihua, Zhou Bin, Wu Guangming
(Tongji Univer sity, Shan ghai 200092, China)
Abstract: Hf O2  sols were prepared by hydrothermal synthesis from HfOCl2·8H2O (precur sor). Hf O2  thin films were f urther prepared via a sp in coatin g method. TEM an d p article size an alyzer were ud to characterize the micro str ucture and particle size distribution of the Hf O2  so ls. It is foun d that the particle size in HfO2 sols can be controlled from abo ut 3 nm to 100 nm via chan ging reaction param eters. The HfO2 an d HfO2-P VP thin films were characterized by ellip someter, atomic for ce microscope (AFM), and Four ier-transform infr ared spectroscopy (FTIR) respectively. The roughn ess of Hf O2-P VP films is less than 0.5 nm and the refractive index is abo ut 1.75. The results sho w that the lar damage threshold of HfO2 f ilm s is higher than 15 J/cm3  (1064 nm, 1 ns), while the lar damage thresho ld for Hf O2-P VP coatin gs can be as high as 20 J/cm3  (1064 nm,
1 ns). The mechanism of the lar damage process of HfO2-PVP coatin gs was also discusd.
Key words: HfO2 films; hy drothermal synthesis; h igh refractive index; HfO2-P VP thin films
CLC number: O484.1 Document code: A Article ID: 1002-185X(2010)S2-052-05
It is well known that optical coatings are generally prepared by the physical vapor deposition (PVD) technology[1]. Recently  sol-gel  techno logy  has  become an effective and competitive alternative. Colloidal-bad HfO2  coatings have unique properties such as nanoscale pores  and  crystallite  s izes.  And  this  wet  chemical coating  technique  is  normally  a  room  temperature process with  less  expensive equipment.  Moreover,  it  is easy for industrial scale up. Sol gel-derived HfO2 coatings are  of  great  technological  interest  in  the  fields  of corrosion protection, nsor films, as well as catalytic films[2-4]. Moreover, with high dielectric constant and high refractive index[5], HfO2 thin films are expected to have important  applications  in  the  field  of  electronics  and optics[6-9]. In the prent paper, HfO2 colloidal suspension was  synthesized  via  a  hydrothermal  process  and  the features of HfO2 and HfO2-PVP coatings were investigated. solution in order to adsorb and remove the acids. At the end of reaction the pH value of the solution was 4.0. The clear solution was held at 150-250 °C for 1-2 h in a stainless steel autoclave coated with Teflon linear. Then it was quenched in an ice-bath to a regular temperature. Finally the water was replaced by 2-methoxyethano l (b.p. 124 °C) by distillation. The clear and stable ethano l sol containing 5wt% HfO2
  with the particle size of about 12 nm was obtained.
the moment of truth
HfO2-PVP  sol  was  obtained  by  adding  different PVP solid content into HfO2 sol. Subquently, HfO2 and HfO2-PVP thin films were deposited on silicon-wafers, K9  glass  or  quartz  glass  us ing  a  spin  coating  method with  the  speed  in  the  range  of  2000-3000  r/min.  The films  were  heated  by  a  heating  plate  with  the  tempe-rature controlled from 80 to 500 °C for 0.5-2 h in air.
2
2.1
Results and Discussions
Effect  of  hydrothermal  s ynthesis  temperature
on the particles size of HfO2 sols
The autoclave was filled to 70 percent of its volume.
1Experimental
HfO2    colloidal  suspension  was  synthesized  via hydrothermal process. A solution of hafnium oxychloride
octahydrate (HfOCl2·8H2O) was first dissolved in water (0.4 mol·dm-3). The pH value of the resultant solution was less than 1.0. Anion exchange res in was added in the The following parameters were t for the hydrothermal synthesis: the precursor concentration of 0.35 mol/L, pH value of 3.5 and time of 42 min. Experiments reveal that
Received date: 2010-04-21
Foundation item: Supported by Chine National Foundation of High Technology (2008AA8041606); Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology (07DZ22302); Shanghai Educational Development Foundation (2007CG26); Program for Young Excellent Talents in Tongji University (2006KJ052)
Corresponding author: Shen Jun, Ph. D., Professor, Pohl Institute of Solid State Physics, Tongji University, Shanghai 200092, P. R. China, Tel/Fax:0086-21-65896071,E-mail:****************
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Shen Jun et al: HfO2 Thin Films Prepared by Hydrothermal Synthesis
the hydrothermal synthesis temperature has an significant effect on the particle size of HfO2 sols (Fig.1).
When the temperature of water was 165 °C, the particle of HfO2 sols was s mall with size around 3 nm. At  this  time, hydrothermal  synthesis  was  not  full y carried out. With increas ing of the hydrothermal synthesis temperature, HfO2 sols particle size incread continually. When the temperature of water reached 180 °C, HfO2 particles mainly distributed in a narrow range around 7 nm. When the  temperature of  water  reached 195 °C, particle distribution curve of HfO2 sols manifest that the particles grew rapidly and distributed in a wider scope. There are two peaks in the HfO2 particle distribution curve. The peaks prent that the particles mainly distributed in 15 and 75 nm around (Fig.1). mol/L  and  pH  value  of  about  0.50,  hydrothermal synthesis reaction would not fully proceed. Therefore, small  particles  with  an  average  size  of  3  nm  in  the solution were obrved. With lowered concentration of the precursor and higher pH value of the solution, the particle size incread in the hydrothermal reaction of the HfO2  sols. The precursor with concentration of 0.35 mol/L  made  sols  with  s maller  particles  mainly  distri-bute  in  a  narrow  range  around  7  nm.  While  the  pre-cursor with concentration of 0.20 mol/L generated the HfO2 so
l of incread particle s ize with a very narrow distribution at around 9 nm, which can be en from the particle size distribution curve.
2.3Effect  of  hydrothermal  synthesis  time  on  the
particle size of HfO2 sol
Hydrothermal synthesis time was changed in order to
2.2 Influence  of  precursor  concentration  on
reaction of the hydrothermal process the
investigate the effect of the time on HfO2 particle size and翻译网
distribution of the sol. Other reaction parameters were
controlled as the precursor concentration of 0.35 mol/L,
the pH value of about    3.5, hydrothermal synthesis
temperature of 180 °C, and 70% of the autoclave filled.
Under longer hydrothermal synthesis time, HfO2  sols’ particle size grew larger, and the particle distribution
became wider (Fig.3). Hydrothermal synthesis process
included an initial generation of the nuclear particles and
a subquent growth in particle s ize. When the
hydrothermal synthesis time was short, the nucleus had
not yet formed or the number of nuclei wasn’t enough.
Conquently, the reaction couldn’t proceed completely
without the precipitation from the HfO2 nucleation.
W hen  the  reactio n  time  was  40  min,  HfO2  s ol particles were mainly distributed around 3 nm. When the
respon time reached 42 min, for mation of a large
number of nuclei in the solution led to a rapid increa in
the concentration till saturation of the HfO2 sols. Con-
quently,  the  sols  had  s mall  particle  s ize  and  narrow
particle  dis tribution.  The  analys is  showed  a  s ma ller
HfOCl2·8H2O  with  different  concentrations,  0.20, 0.35, and 0.50 mol/L, were prepared respectively, with the autoclave filled in 70%, hydrothermal temperature of 180 °C and reaction time of 42 min. Subquently, the effect  of  the  precursor  concentration  on  HfO2  particle size distribution was investigated.
W hen  other  conditions  were  s et,  the  precu rsor concentration has great influence on the s ize of particles in the sol (Fig.2). With precursor concentration of 0.50
Particle Size/nm
Fig.1    Particles size distribution of HfO2 sols at different
hydrothermal synthesis temperatures
particle distribution in HfO  sol with the major particle
2
5
5
4
4
3
3
2
2
1
1
P article Size/n m
Particle Size/nm
90 100
Fig.2    Particle size distribution of HfO2 sol with differ ent
precursor concentration
Fig.3    Particle size distribution of HfO2 sol for different
hydrothermal synthesis time V
o
l
u
m
e
/
%
V
o
l
u
m
e
/
%
V
o
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u
m
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/
%
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稀有金属材料与工程 第 39 卷
size  at around  7 nm. larger  HfO 2    particle Meanwh ile,  the  reaction  showed size  and  incread  number  of    2.4 Effect of pH value on the hydrothermal synthesis
time of ideal HfO 2 sol
The  quality  ratio  of  ion  exchange  resin  to particles. The main reason was that HfO 2  particles grew  up and clustered gradually due to high temperature and high pressure. This reason lead to increa in the particle size and the clustering process of particles.
The particle continuously incread in size and its distribution range became wider with the extension of  hydrothermal synthesis time. When the respon time  reached 45 min, the sol particle distribution curve had two distribution peaks: around 9 and 20 nm. Hydro- thermal synthesis time of 50 min also resulted in particle  size distribution curve with two peaks at about 15 and 70 nm. HfO 2 sol particles were mainly distributed in about 40 nm with wider size distribution at reaction time of 55 min.
TEM images in Fig.4 prents a gradual growth in sol particles in increasing hydrothermal synthesis time. At the same time, the particles clustered and the cluster size  incread  as  the  reaction  time  incread.  Finally, some  large  s ize  hard  clusters  could  be  formed.  The hard  clusters  would  influence  the  sol  properties,  evenmelampus
leading to the sols no longer uful for coating.
precursors quality was changed to adjust the solution pH value. W ith 70% of the autoclave filled, the precursor concentration of 0.35 mol/L, and the hydrothermal temperature of 180 °C, the influence of pH value on the hydrothermal synthesis process was also investigated (Table 1).
The hydrothermal synthesis time of the ideal sols  incread as a result of a decrea in the pH value. Due  to the existence of H +, the induced time was extended  and the efficiency was reduced for the hydrothermal synthesis. Eventually, we could u the previous ly mentioned  parameters  to  optimize  the  preparation conditions for the targeted HfO 2 sols.
2.5 Influence of coating technology on the refractive
index  Effect  of  different  coating  speed  on  the  film refractive  index  and  the  thickness  was  investigated. HfO 2 thin films were coated on different substrates with different speeds and the resultant films were annealed in the same heating treatment process. The refractive index and the thickness of the thin films were examined by ellipsometer.
The speed of the spin coating machine had impact on the refractive index and the thickness of HfO 2  thin film. A higher speed led to a dry film before reaching the desired speed. Conquently, further higher speed had no significant influence on the thickness of HfO 2 thin film (Fig.5). We assumed th
at there was no simple linear  relationship between the thickness of the films and the rotational speed of the spin coater.
2.6    Influence of the accession of PVP on the HfO 2
films refractive index
Table 2 displays the effect of PVP content on the film refractive index and the thickness. With the increa of the PVP content in the sol, refractive index of films  became too higher.
When the PVP/HfO 2  (mass ratio) reached to 10%, the refractive index of HfO 2-PVP film was 1.75, much  higher  than  that  of  HfO 2  thin  film  (1.630).  However, with  further  increa  of  PVP,  the  refractive  index  of
a
Table 1    E ffect of pH value on the hydrothermal time
1:2 2:3 1:1 2:1 1:0
HfOCl 2·8H 2O :
Anion-exchan ge resin
2.33    2.03    1.80    1.60    0.76 pH value of HfOCl 2
aqueo us solution Hydrothermal Fig.4    TEM images of Hf O 2 sols with differ ent hydrother-
mal synthesis time: (a) 40 min, (b) 50 min, and (c) 55 min
26
28
30
32
42
synthesis time/min
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·55·
新课标英语听力下载
Shen Jun et al : HfO 2 Thin Films Prepared by Hydrothermal Synthesis
temperature should not exceed 300 °C when the organic binder PVP was ud in the HfO 2 film. 2.8    HfO 2-PVP film morphology
The surface toughness R a of HfO 2-PVP thin films  were  different  (Fig.7)  at  various  temperatures.  The organic ingred ients in the pores of HfO 2-PVP thin film burned gradually at that increas ing temperature. When  the temperature reached 450 °C, some HfO 2  particles in the thin film grew larger and crystallized. This is the reason  why  the  R a    values  of  HfO 2-PVP  thin  film incread to 0.798 nm at 450 °C.
2.9 Effect of the accession PVP on the lar damage threshold of HfO 2-PVP film
In  the  HfO 2-PVP  film,  PVP  wrapped  the  HfO 2
particles. Therefore, in the lar irradiation, PVP  functioned to protect HfO 2 particles. Becau of its  flexibility, PVP could easily reduce the lar impact on 1.640
70
Thickness  o f H fO 2 thin fil m Refractive index o f H fO 2 thin fil m
1.635 65    1.630curtain什么意思
60    1.625 55    1.620 50    1.615
accountant是什么意思
45
1.610
2    3    4
连衣裙英文Speed of Spin-Coatin g/×103 r·min -1
Fig.5    Effect of the rotational speed on the film thickness
and refractive in dex
T able 2    Influence of the PVP/ HfO 2 mass ratio on
英语音标视频下载HfO 2-PVP thin films thickness and refrac- tive index
Mass r atio of PVP/ HfO 2  Refractive index  Thickness/nm
the HfO  films and thermal stress inside the film. The 2 100/0
5/100 10/100 15/100
20/100
1.590
1.736 1.750 1.743 1.730
45.12 76.34 81.18 73.26 74.61
experiments showed that the lar damage threshold of the HfO 2-PVP film was 20 J/cm 2  (1064 n
m, 1ns, with 150 °C heating treatment), higher than the as-prepared  HfO 2 thin film of 15 J/cm 2 (1064 nm, 1ns).
HfO 2-PVP film dropped  slightly.  This  is  becau  PVP  had relatively low refractive index contrast with HfO 2 skeleton.
2.7 FTIR of HfO 2-PVP film
The infrared spectra of HfO 2-PVP thin film with different temperature of heat treatment manifes ted different pecks (Fig.6). As shown in the infrared spectra, when the heating temperature incread, some infrared absorption peaks (between 1292 and 1662 cm -1) corre- sponding to various organic groups were weakened. This could be explained by the gradual burn ing out of organic ingredients in the film at high-temperature. When the temperature  reached  450  °C,  the  absorptio n  peaks    a
R a =0.410 nm
ovaleb
cm -1 between  1292 and  1662 disappeared.  The  main reason  was  that organic  solvents  and  PVP in  the  film burned out at a high temperature. Clearly, the treating
R a =0.653 nm
c
450 °C
300 °C 150 °C
3000
665
3400
1292
R a =0.798 nm
1600
500
1500 2500
3500
4500
Fig.7 AFM photos of HfO 2-PVP thin films after different
heating treatment at different temperatures: (a) 150 °C, (b) 300°C, and (c) 450 °Cdemanding
Waven um ber/cm -1
Fig.6    FTIR spectra of HfO 2-P VP thin films
T r a n s m i t t a n c e /a .u
T h i c k n e s s /n m
R e f r a c t i v e  I n d e x
·56·稀有金属材料与工程第39 卷
3Conclusions
Ideal  HfO2  sol
286(1-2): 127
[3]  Mehner  A,  Klumper-Westkamp  H,  Hoffmann  F  et  al.  Thin
Solid Films[J], 1997, 308-309: 363
[4]  Montesperelli  G,  Pumo  A  et  al.  Sensors  and  Actuators  B:
Chemica l[J], 1995, 25(1-3): 705
[5] Luo Aiy un, Shen Jun, Yan g Fan et al. High Power La r and
Particle Beams[J], 2006, 18(9): 1486
[6] Xu Xian g, Zhou Bin, Liu Ch unze et al. Journal of Inorganic
Materia ls[J], 2006, 21(3): 753
[7] Rainer F, De Marco F P, Staggs M C et al. Proc SPIE[J], 1994,
2114(9): 9
[8] Floch H G, Bellev ille P F. Proc SPIE[J], 1996, 2714(521): 521
[9] Thomas I M. Proc SPIE[J], 1994, 2288(50): 50
[10] Wang Shen gzh ao(王生钊), Sh en Jun(沈军) et al. Jou rnal of
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35(12): 1666
was  obtained  via  hydrothermal
with  the  optimum  reaction  para-
synthesis  technology
meters concluded in  the paper. Colloid-bad HfO2 and
HfO2-PVP high refractive index coatings[10] were prepared
on  glass  substrates  by  spin-coating  techno logy.  The
features of HfO2-PVP coatings by different temperature
treatments were investigated for a desired R a  of around
0.4  nm.  Lar  damage  threshold  of  20  J/cm2    for
HfO2-PVP coatings was achieved using high power lar
at the wavelength of 1064 nm and puls width of 1 ns.
References
[1] Sh en Jun, Zhan g Qinyuan, Wan g Jue et al. Jou rnal of Sol-Gel
Science and Technology[J], 2000, 19(1-3): 271
[2] Di Maggio R, Rossi S, Scar di P. Thin Solid Film s[J], 1996,
水热合成法制备HfO2 薄膜
沈军,王生钊,王晓栋,张志华,周斌,吴广明
(同济大学,上海200092)
摘要:以HfOCl2·8H2O 为前驱体采用水热合成法制备了HfO2 溶胶,采用旋涂法制备了HfO2-P VP 薄膜。利用透射电镜和粒度分析仪观察和表征Hf O2 溶胶的微观结构和粒度分布。实验发现,通过调整不同的水热合成温度、反应物前驱体浓度、溶液的pH 值和水热合成时间等制备条件,可以在3~100  nm 范围内对Hf O2 溶胶颗粒的大小进行控制。分别采用椭偏仪,原子力显微镜,傅里叶红外变换光谱对Hf O2–PVP 薄膜的形貌和结构进行了表征和测量。结果表明,旋涂法制备的Hf O2-P VP 薄膜的粗糙度小于0.5 nm,折射率达1.75 左右。实验还发现,HfO2 薄膜的激光损伤阈值达到15 J/cm3(1064 nm,1 ns),Hf O2-P VP 薄膜的激光损伤阈值可高达20 J/cm3 (1064 nm,1 ns)。还对HfO2-P VP 薄膜中有机粘结剂PVP 在激光诱导损伤过程中的作用机理进行了初步探讨。关键词:Hf O2 薄膜;水热合成;高折射率;HfO2-P VP 薄膜
作者简介:沈军,男,1967 年生,博士,教授,博士生导师,同济大学波耳固体物理研究所,上海200092,电话/传真:************,E-mail: sh enjj@on

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