Role of HCl in Atomic Layer Deposition of TiO₂ Thin Films from Titanium Tetrachloride and Water

Leem, Jina,Park, Inhye,Li, Yinshi,Zhou, Wenhao,Jin, Zhenyu,Shin, Seokhee,Min, Yo-Sep Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.4

Atomic layer deposition (ALD) of $TiO_2$ thin film from $TiCl_4$ and $H_2O$ has been intensively studied since the invention of ALD method to grow thin films via chemical adsorptions of two precursors. However the role of HCl which is a gaseous byproduct in ALD chemistry for $TiO_2$ growth is still intriguing in terms of the growth mechanism. In order to investigate the role of HCl in $TiO_2$ ALD, HCl pulse and its purging steps are inserted in a typical sequence of $TiCl_4$ pulse-purge-$H_2O$ pulse-purge. When they are inserted after the first-half reaction (chemisorption of $TiCl_4$), the grown thickness of $TiO_2$ becomes thinner or thicker at lower or higher growth temperatures than $300^{\circ}C$, respectively. However the insertion after the second-half reaction (chemisorption of $H_2O$) results in severely reduced thicknesses in all growth temperatures. By using the result, we explain the growth mechanism and the role of HCl in $TiO_2$ ALD.

Role of HCl in Atomic Layer Deposition of TiO2 Thin Films from Titanium Tetrachloride and Water

Jina Leem,Inhye Park,Yinshi Li,Wenhao Zhou,Zhenyu Jin,Seokhee Shin,민요셉 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.4

Atomic layer deposition (ALD) of TiO2 thin film from TiCl4 and H2O has been intensively studied since the invention of ALD method to grow thin films via chemical adsorptions of two precursors. However the role of HCl which is a gaseous byproduct in ALD chemistry for TiO2 growth is still intriguing in terms of the growth mechanism. In order to investigate the role of HCl in TiO2 ALD, HCl pulse and its purging steps are inserted in a typical sequence of TiCl4 pulse-purge-H2O pulse-purge. When they are inserted after the first-half reaction (chemisorption of TiCl4), the grown thickness of TiO2 becomes thinner or thicker at lower or higher growth temperatures than 300 oC, respectively. However the insertion after the second-half reaction (chemisorption of H2O) results in severely reduced thicknesses in all growth temperatures. By using the result, we explain the growth mechanism and the role of HCl in TiO2 ALD.

Charge trapping behavior in organic–inorganic alloy films grown by molecular layer deposition from trimethylaluminum, <i>p</i>-phenylenediamine and water

Zhou, Wenhao,Leem, Jina,Park, Inhye,Li, Yinshi,Jin, Zhenyu,Min, Yo-Sep The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.45

<P>Organic–inorganic hybrid or alloy films have great potential as a functional material because they have structural flexibility owing to the presence of an organic moiety. Here organic–inorganic hybrid films were grown by molecular layer deposition (MLD) by using trimethylaluminum and <I>p</I>-phenylenediamine. Although the hybrid films could be grown <I>via</I> the self-limiting growth mechanism of MLD, the hybrid films were severely air sensitive. The stability problem of the hybrid films could be solved by alloying the hybrid layer with Al<SUB>2</SUB>O<SUB>3</SUB> layers. The alloy films, which were grown by repeating supercycles with one subcycle for the hybrid layer and four subcycles for the Al<SUB>2</SUB>O<SUB>3</SUB> layers, showed excellent dielectric properties: a leakage current density of ∼2.3 × 10<SUP>−8</SUP> A cm<SUP>−2</SUP> at 1 MV cm<SUP>−1</SUP>; a dielectric breakdown field at ∼2.9 MV cm<SUP>−1</SUP>; and a dielectric constant of ∼6.2. Interestingly, charge trapping behavior was clearly observed in the alloy film. The charge trapping ability of the alloy film was verified with a charge trapping memory capacitor in which the alloy film was inserted as a charge trapping layer.</P> <P>Graphic Abstract</P><P>Organic–inorganic hybrid or alloy films have great potential as a functional material because they have structural flexibility owing to the presence of an organic moiety. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm35553a'> </P>

Modified Shrinking Core Model for Atomic Layer Deposition of TiO2 on Porous Alumina with Ultrahigh Aspect Ratio

Inhye Park,Jina Leem,Hoo-Yong Lee,민요셉 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

When atomic layer deposition (ALD) is performed on a porous material by using an organometallic precursor, minimum exposure time of the precursor for complete coverage becomes much longer since the ALD is limited by Knudsen diffusion in the pores. In the previous report by Min et al. (Ref. 23), shrinking core model (SCM) was proposed to predict the minimum exposure time of diethylzinc for ZnO ALD on a porous cylindrical alumina monolith. According to the SCM, the minimum exposure time of the precursor is influenced by volumetric density of adsorption sites, effective diffusion coefficient, precursor concentration in gas phase and size of the porous monolith. Here we modify the SCM in order to consider undesirable adsorption of byproduct molecules. TiO2 ALD was performed on the cylindrical alumina monolith by using titanium tetrachloride (TiCl4) and water. We observed that the byproduct (i.e., HCl) of TiO2 ALD can chemically adsorb on adsorption sites, unlike the behavior of the byproduct (i.e., ethane) of ZnO ALD. Consequently, the minimum exposure time of TiCl4 (~16 min) was significantly much shorter than that (~ 71 min) of DEZ. The predicted minimum exposure time by the modified SCM well agrees with the observed time. In addition, the modified SCM gives an effective diffusion coefficient of TiCl4 of ~1.78 × 10−2 cm2/s in the porous alumina monolith.

Modified Shrinking Core Model for Atomic Layer Deposition of TiO₂ on Porous Alumina with Ultrahigh Aspect Ratio

Park, Inhye,Leem, Jina,Lee, Hoo-Yong,Min, Yo-Sep Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

When atomic layer deposition (ALD) is performed on a porous material by using an organometallic precursor, minimum exposure time of the precursor for complete coverage becomes much longer since the ALD is limited by Knudsen diffusion in the pores. In the previous report by Min et al. (Ref. 23), shrinking core model (SCM) was proposed to predict the minimum exposure time of diethylzinc for ZnO ALD on a porous cylindrical alumina monolith. According to the SCM, the minimum exposure time of the precursor is influenced by volumetric density of adsorption sites, effective diffusion coefficient, precursor concentration in gas phase and size of the porous monolith. Here we modify the SCM in order to consider undesirable adsorption of byproduct molecules. $TiO_2$ ALD was performed on the cylindrical alumina monolith by using titanium tetrachloride ($TiCl_4$) and water. We observed that the byproduct (i.e., HCl) of $TiO_2$ ALD can chemically adsorb on adsorption sites, unlike the behavior of the byproduct (i.e., ethane) of ZnO ALD. Consequently, the minimum exposure time of $TiCl_4$ (~16 min) was significantly much shorter than that (~71 min) of DEZ. The predicted minimum exposure time by the modified SCM well agrees with the observed time. In addition, the modified SCM gives an effective diffusion coefficient of $TiCl_4$ of ${\sim}1.78{\times}10^{-2}\;cm^2/s$ in the porous alumina monolith.

Characteristics of Nitride-Based Laser Diode Grown on SiO2-Removed Laterally Overgrown GaN

윤호 최,Hee-Suk Song,Hwan Kuk Yuh,Jae Hyung Yi,Jina Jeon,Junghoon Lee,Min Hong Kim,Shi-Jong Leem,Sungwon Khym 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III

Systematic study on SiO$_2$-removed laterally epitaxially overgrown (SR-LEO) GaN layers was carried out to determine the effects of SiO$_2$ removal and thermal annealing. After the first phase of SR-LEO preparation when the growth is stopped just before coalescence of adjacent wings, X-ray diffraction (XRD) measurements showed broad split peaks with tilting angle of about 0.5$^\circ$. After the oxide masks were etched away the broad peaks were replaced by sharp peaks with tilting angle of only about 0.2$^\circ$, suggesting elastic deformation originating from the interface between overgrown GaN and SiO$_2$ mask to be a major source of crystallographic tilting in conventional LEO layers. The low-angle tilt is attributed to plastic deformation from in-plane defects that arise during the initial lateral growth phase and residual elastic deformation within the wing region. In order to assess the practicality of this novel LEO technique for device applications, a SR-LEO GaN was used as a base layer to fabricate index guided laser diodes with cavity length of 500 $\mu$m and ridge width of 2.3 $\mu$m. Under continuous wave operation at room temperature, the threshold current was 68 mA, which corresponded to a threshold current density of 5.9 kA/cm$^2$, and the operating voltage at threshold was 5.3 V.