Jane P. Chang

University of California, Los Angeles, Los Angeles, CA, United States

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Publications (70)162.34 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Thin films of a solid electrolyte, lithium aluminosilicate, were synthesized by atomic layer deposition (ALD) for potential applications in 3D Li-ion microbatteries. The films were deposited at 290 °C via alternating the ALD growth of the constituents, LiOH, Al2O3 and SiO2. Manipulation of the cation composition and thickness was achieved through well-controlled surface reactions during each precursor pulse cycle. Various compositions were obtained by changing the number of pulse cycles for each precursor, which enabled lithium aluminate (LixAlyO), lithium aluminosilicate (LixAlySizO) and stoichiometric LiAlSiO4 materials to be prepared. The as-deposited ALD films were amorphous and formed conformal coatings over Si nanowires. Films as thin as 6 nm were found to be free of pinholes. Complex impedance measurements confirmed that the films were ionic conductors with the room temperature conductivity in the range of 10−7 to 10−9 S cm−1 and an activation energy between 0.46 and 0.84 eV, depending upon the film composition.
    J. Mater. Chem. A. 06/2014; 2(25).
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    ABSTRACT: The effect of oxygen addition to chlorine plasma during shallow trench isolation etching is quantified in this work. Specifically, the electron density and the electron temperature in an electron cyclotron resonance reactor were characterized by a Langmuir probe and were found to remain relatively constant upon O2 addition. The silicon etching rates were found to increase with the square root of the ion energy, suggesting the etching reaction is limited by the momentum transfer from ions to the surface. A relatively small amount of oxygen addition (<10%) to the chlorine plasma simultaneously changes the reactor wall conditions and surface kinetics, since oxygen becomes actively involved in the surface reactions. The change in the chamber wall conditions and surface kinetics leads to the change in both the amount of etch products and the etched feature profile. The incorporation of oxygen on the surface results in a significant change of the etched surface morphology and its composition. This work suggests a small amount of O2 addition to Cl2 plasmas in shallow trench isolation etching changes the etching behavior primarily through modifying the kinetics on etched surfaces. A multiscale etch model consisting of translating mixed layer and Monte Carlo modules for bulk and feature scale etching, respectively, was successfully applied to this case, demonstrating good agreement with the experimental results.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2013; 31(4):042201-042201-12. · 1.36 Impact Factor
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    ABSTRACT: The incubation time during atomic layer deposition (ALD) of lead oxide, zirconium oxide, and titanium oxide on each other was quantified in order to precisely control the composition of lead zirconate titanate (PZT). The desired stoichiometry of Pb:Zr:Ti=2:1:1, which yields the desired ferroelectricity, was found to depend strongly on the ALD sequence, the substrate of choice, as well as the postdeposition annealing temperature. With the desired stoichiometry, the ferroelectric and piezoelectric properties of the PZT films were validated by polarization–voltage hysteresis loop and piezoresponse force microscopy, respectively, demonstrating that ALD method is a viable technique for ultra thin ferroelectric films for device applications.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2013; 31(1):2207-. · 1.36 Impact Factor
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    ABSTRACT: Rare-earth (RE = Eu, Dy, Tb, and Ce) ion doped core and core–shell LaPO4 phosphors were synthesized to elucidate the effect of spatial distribution of dopants on the emission spectra. The core–shell architecture was designed as a single particle that can be excited by a single wavelength and yield a balanced white light appearance with long emission lifetimes. Specifically, a multishell architecture was employed to separate the Eu3+ and Tb3+ within the phosphor to circumvent the energy transfer between them, passivate the surface quenching sites, and control Ce3+ doping to sensitize other RE ions. To assess the effectiveness of these core–shell phosphors, the International Commission on Illumination (CIE) coordinates and luminescence lifetimes are quantified as the figures of merit. The Eu3+:LaPO4|Ce3+,Dy3+:LaPO4|Tb3+:LaPO4 layering resulted in CIE coordinates of (0.34, 0.35) using 365 nm excitation, nearly at center of the white light regime at (0.35, 0.35). Finally, the emission lifetimes were measured to be 0.85, 4.34, and 3.26 ms and resulted in a total increase of 31, 36, and 16% over the RE3+:LaPO4 reference phosphors, where RE = Dy, Tb, and Eu, respectively. The synthesized phosphor material has high-quality white light with improved emission lifetimes, suitable for application in white light LED devices.
    The Journal of Physical Chemistry C. 06/2012; 116(23):12854–12860.
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    ABSTRACT: Rare-earth (RE) (Er3+ and Yb3+, Er3+)-doped yttrium oxide (Y2O3) core–shell particles were synthesized in this work using a two-step process where the cores were formed by molten salt synthesis while the shell was deposited by a sol–gel process. The cores were 100–150 nm, and a shell layer, up to 12 nm thick, was controllable based on the mass ratio between the RECl3 salts and the Er3+:Y2O3 (1 mol %) particles. A passive Y2O3 shell layer, at an optimal thickness around 8 nm, passivated the surface quenching sites and resulted in a 53% increase in photoluminescence lifetimes and visible separation in Stark splitting. Optically active shell layers, such as Yb2O3 and Yb3+:Y2O3, not only passivated the quenching sites but also facilitated energy transfer between the spatially controlled RE ions. Furthermore, the effect of surface passivation on the upconversion luminescence was determined through the purposed dynamic processes to corroborate the effect of the hydroxyl groups on energy dissipation. The addition of a passive shell layer or a sensitizer reduced the upconversion to a two-photon process due to a decreased branching ratio at the 4I11/2 energy level. Yb2O3 is deemed the most effective shell material due to the largest increase photoluminescence intensity at 1535 nm as a function of the pump power and the lifetime of the 4S3/2 radiative transition, important in upconversion luminescence. The increased lifetime and low pump power achieved with Er3+:Y2O3|Yb2O3 core–shell phosphors hold promise in lighting devices for improved overall device efficiency.
    The Journal of Physical Chemistry C. 04/2012; 116(18):10333–10340.
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    ABSTRACT: To predict and optimize luminescence efficiency of rare-earth ion doped (RE) nanophosphors, a relationship between the RE-concentration and the luminescent parameters is often obtained by Judd-Ofelt analysis, where the quality factor (χ = Ω4/Ω6) depends on the Er interactions with other RE elements in the second nearest neighboring shell. In this work, a detailed analysis of the local bonding environment by extended x-ray absorption fine structure (EXAFS) analyses is shown as effective as the Judd-Ofelt analysis to quantify the Er↔RE interaction in the second nearest neighboring shell (ρN = IREr↔RE2/IREr↔RE1). As the physical basis of ρN is consistent to that of χ, the EXAFS analysis becomes a viable alternative to replace Judd-Ofelt analysis to predict the optimum dopant concentration. This approach was corroborated based on analysis of Er3+:Y2O3 and core-shell Er3+:Y2O3|Y2O3 (5 nm shell) nanoparticles (NPs), with Er3+ concentrations up to 20 mol %. The ρN ratio from EXAFS analysis was shown to strongly correlate to the lifetimes extracted from the Judd-Ofelt analysis, both predicting the optimal dopant concentrations to be at 5 mol % and 2 mol % for the Er3+:Y2O3 and core-shell NPs, respectively. This confirms that EXAFS analysis can be used as a more time efficient method to achieve the same outcome typically obtained by Judd-Ofelt analysis, enabling the optimization of the luminescent lifetimes of RE doped nano-phosphors.
    Journal of Applied Physics 04/2012; 111(8). · 2.21 Impact Factor
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    ABSTRACT: Di-block copolymer synthesized Co/Al2O3 core-shell nanocrystal (NC) capacitors were fabricated in order to study the temperature-dependent electron transport. The capacitance-voltage memory window is shown to increase proportionally with the substrate temperature, saturating at 3.5 V, at 175 °C. At elevated operating temperatures, the tunneling of electrons increases, resulting in large flatband voltage shift. Furthermore, the electron leakage of the NCs at high temperature is faster than the leakage at room temperature due to thermally assisted tunneling. The activation energy is determined by exponentially fitting the thermally dependent retention performance, which was then used to model the occupied energy levels and further elucidate the electron transport within the NC memory.
    Journal of Applied Physics 03/2012; 111(6). · 2.21 Impact Factor
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    ABSTRACT: Tin (Sn) crystal growth on Sn-based anodes in lithium ion batteries is hazardous for reasons such as possible short-circuit failure by Sn whiskers and Sn-catalyzed electrolyte decomposition, but the growth mechanism of Sn crystals during battery cycling is not clear. Here we report different growth mechanisms of Sn crystal during the lithiation and delithiation processes of SnO(2) nanowires revealed by in situ transmission electron microscopy (TEM). Large spherical Sn nanoparticles with sizes of 20-200nm grew instantaneously upon lithiation of a single-crystalline SnO(2) nanowire at large current density (j>20A/cm(2)), which suppressed formation of the Li(x)Sn alloy but promoted agglomeration of Sn atoms. Control experiments of Joule-heating (j≈2400A/cm(2)) the pristine SnO(2) nanowires resulted in melting of the SnO(2) nanowires but not Sn particle growth, indicating that the abnormal Sn particle growth was induced by both chemical reduction (i.e., breaking the SnO(2) lattice to produce Sn atoms) and agglomeration of the Sn atoms assisted by Joule heating. Intriguingly, Sn crystals grew out of the nanowire surface via a different "squeeze-out" mechanism during delithiation of the lithiated SnO(2) nanowires coated with an ultra-thin solid electrolyte LiAlSiO(x) layer. It is attributed to the negative stress gradient generated by the fast Li extraction in the surface region through the Li(+)-conducting LiAlSiO(x) layer. Our previous studies showed that Sn precipitation does not occur in the carbon-coated SnO(2) nanowires, highlighting the effect of nanoengineering on tailoring the electrochemical reaction kinetics to suppress the hazardous Sn whiskers or nanoparticles formation in a lithium ion battery.
    Micron 02/2012; 43(11):1127-33. · 1.88 Impact Factor
  • Nathan Marchack, Jane P Chang
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    ABSTRACT: The invention of the transistor followed by more than 60 years of aggressive device scaling and process integration has enabled the global information web and subsequently transformed how people communicate and interact. The principles and practices built upon chemical processing of materials on silicon have been widely adapted and applied to other equally important areas, such as microfluidic systems for chemical and biological analysis and microscale energy storage solutions. The challenge of continuing these technological advances hinges on further improving the performance of individual devices and their interconnectivity while making the manufacturing processes economical, which is dictated by the materials' innate functionality and how they are chemically processed. In this review, we highlight challenges in scaling up the silicon wafers and scaling down the individual devices as well as focus on needs and challenges in the synthesis and integration of multifunctional materials.
    Annual Review of Chemical and Biomolecular Engineering 01/2012; 3:235-62. · 7.51 Impact Factor
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    ABSTRACT: Atomic layer deposited (ALD) Pb(Zr,Ti)Ox (PZT) ultra-thin films were synthesized on an ALD Al2O3 insulation layer on 4H-SiC substrate for metal-ferroelectric-insulator-semiconductor (MFIS) device applications. The as-deposited PZT was amorphous but crystallized into a perovskite polycrystalline structure with a preferred [002] orientation upon rapid thermal annealing (RTA) at 950 °C. The capacitance-voltage and current-voltage characteristics of the MFIS devices indicate carrier injection to the film induced by polarization and Fowler-Nordheim (FN) tunneling when electric field was high. The polarization-voltage measurements exhibited reasonable remanent and saturation polarization and a coercive electrical field comparable to that reported for bulk PZT. The piezoresponse force microscope measurements confirmed the polarization, coercive, and retention properties of ultra-thin ALD PZT films.
    Journal of Applied Physics 06/2011; 109(12):124109-124109-4. · 2.21 Impact Factor
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    ABSTRACT: An ordered Co/Al2O3 core-shell nanocrystal (NC) nonvolatile memory device was fabricated. Self-assembled diblock copolymer process aligned the NCs with uniform size. Co/Al2O3 core-shell NCs were formed using atomic layer deposition of Al2O3 before and after the ordered Co NC formation. Compared to Co NC memory, Co/Al2O3 core-shell NC memory shows improved retention performance without sacrificing writing and erasing speeds.
    Applied Physics Letters 05/2011; 98(19):192107-192107-3. · 3.79 Impact Factor
  • Nathan Marchack, Jane P Chang
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    ABSTRACT: Plasmas have been widely utilized to pattern various materials, from metals to semiconductors and oxides to polymers, for a vast array of applications. The interplay between physical, chemical and material properties that comprises the backbone of plasma etching is discussed in this perspective paper, with a focus on the needed tools and approaches to address the challenges facing plasma etching and to realize the desired pattern transfer fidelity at the nanoscale.
    Journal of Physics D Applied Physics 04/2011; 44(17):174011. · 2.53 Impact Factor
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    ABSTRACT: The hydrothermal growth of yttrium hydroxide [Y(OH)3] nanotubes (NTs) and the subsequent transformation into yttrium oxide (Y2O3) NTs by thermal annealing were probed by in situ characterization techniques, mainly with synchrotron radiation, to elucidate its reaction mechanism. Upon heating the precursors to 120 °C, the formation of Y(OH)3 NTs was immediately observed, as evident by the diffraction peaks related to the hexagonal phase of Y(OH)3. However, on the basis of X-ray absorption spectroscopic data, the local bonding and ordering began to resemble those of a stable Y(OH)3 crystal after a reaction time of 7 h. Upon annealing of the as-prepared Y(OH)3 NTs, a stable reaction intermediate, YO(OH), with a monoclinic crystal structure is formed at 250 °C. Hence, the dehydration process follows a two-step reaction: Y(OH)3 → YO(OH) → Y2O3; i.e. the elimination of the hydroxyl groups takes two sequential steps, which leads to the formation of Y2O3 NTs.
    The Journal of Physical Chemistry C. 09/2010; 114(41).
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    ABSTRACT: The semiconductor industry will soon be launching 32 nm complementary metal oxide semiconductor (CMOS) technology node using 193 nm lithography patterning technology to fabricate microprocessors with more than 2 billion transistors. To ensure the survival of Moore's law, alternative patterning techniques that offer advantages beyond conventional top-down patterning are aggressively being explored. It is evident that most alternative patterning techniques may not offer compelling advantages to succeed conventional top-down lithography for silicon integrated circuits, but alternative approaches may well indeed offer functional advantages in realising next-generation information processing nanoarchitectures such as those based on cellular, bioinsipired, magnetic dot logic, and crossbar schemes. This paper highlights and evaluates some patterning methods from the Center on Functional Engineered Nano Architectonics in Los Angeles and discusses key benchmarking criteria with respect to CMOS scaling.
    Advanced Materials 02/2010; 22(6):769-78. · 14.83 Impact Factor
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    ABSTRACT: Thin films of SrHfO3 have been grown by MBE on Si (001). Synchrotron X-ray diffraction (XRD) and grazing incidence extended X-ray absorption spectroscopy (GI-EXAFS) were employed to elucidate the epitaxial relationship between the SrHfO3 and Si (001). The SrHfO3 film was unstrained and exhibited a lattice mismatch of 6% with silicon; the orientation was SrHfO3(001)[110] || Si(001)[100]. The SrHfO3 (200) plane demonstrated the expected four fold symmetry with a peak positioned every 90° in the phi scan of X-ray diffraction. Excellent fits of the GI-EXAFS showed that Hf was coordinated to about 6 oxygen atoms at a bonding distance of 2.080 Å and about 8 Sr neighbors at 3.53 Å. The short range order determined by GI-EXAFS corroborated the long range order determined by XRD, where nearly epitaxial growth, good crystalline quality, low disorder and minimal defects observed make SrHfO3 a viable dielectric candidate in Si based complementary metal-oxide-semiconductor field effect transistors.
    Thin Solid Films 01/2010; 518(6). · 1.87 Impact Factor
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    ABSTRACT: The luminescent properties, including cathodoluminescence and photoluminescence, of the erbium-doped yttrium oxide ( Er <sup>3+</sup>: Y <sub>2</sub> O <sub>3</sub>) nanotubes (NTs) have been systematically studied. These NTs were synthesized by a hydrothermal treatment followed by a dehydration process. Cathodoluminescent measurements show that every Er <sup>3+</sup>: Y <sub>2</sub> O <sub>3</sub> NT is luminescent under electron excitation. In the near-infrared region, sharp, well-resolved, pump-power-dependent, and thermally stable photoluminescence was observed from ensemble NTs. Individual NTs also present characteristic luminescent emissions in the same spectral region. These properties make these NTs promising for applications in display, bioanalysis, and telecommunication.
    Journal of Applied Physics 06/2009; · 2.21 Impact Factor
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    ABSTRACT: In this paper, the luminescence, including photoluminescence, upconversion and cathodoluminescence, from single-crystalline erbium-doped yttria nanoparticles with an average diameter of 80 nm, synthesized by a molten salt method, is reported. Outstanding luminescent properties, including sharp and well-resolved photoluminescent lines in the infrared region, outstanding green and red upconversion emissions, and excellent cathodoluminescence, are observed from the nanocrystalline erbium-doped yttria. Moreover, annealing by the high power laser results in a relatively large increase in photoluminescent emission intensity without causing spectral line shift. These desirable properties make these nanocrystals promising for applications in display, bioanalysis and telecommunications.
    Advanced Functional Materials 02/2009; 19(5):748 - 754. · 10.44 Impact Factor
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    ABSTRACT: This work focuses on the synthesis of nanocrystals with A2B2O7 composition (in this study, A = La, Er, or their mixture, B = Zr, Hf, or their mixture), their structural characterization, and luminescent property measurements. It was necessary to utilize a single-source complex precursor A(OH)3·BO(OH)2·nH2O to synthesize these A2B2O7 nanocrystals, by the synergistic interplay between the reduction of the transport distances of the reactive constituents to an atomic length scale and the enhanced diffusion of the reactants in the molten salt medium. This process is highly generalizable for the preparation of other complex oxide nanocrystals. Moreover, these nanocrystals possess outstanding luminescent properties, including strong photoluminescence in the infrared region, efficient pump-power dependence and excellent cathodoluminescence. These desirable properties make these nanocrystals promising for applications in display, bioanalysis, lighting, scintillating, and telecommunications.
    Journal of Physical Chemistry C - J PHYS CHEM C. 01/2009; 113(4):1204-1208.
  • Jane P. Chang, Hans-Olof Blom, Ryan M. Martin
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    ABSTRACT: The mechanism for ion-enhanced chemical etching of hafnium aluminate thin films in Cl/BCl plasmas was investigated in this work, specifically how the film composition, ion energy, and plasma chemistry determine their etch rates. Several compositions of Hf{sub 1-x}AlO{sub y} thin films ranging from pure HfO to pure AlO were etched in BCl/Cl plasmas and their etch rates were found to scale with (E{sub ion}) in both Cl and BCl plasmas. In Cl plasmas, a transition point was observed around 50 eV, where the etch rate was significantly enhanced while the linear dependence to (E{sub ion}) was maintained, corresponding to a change in the removal of fully chlorinated to less chlorinated reaction products. In BCl plasma, deposition dominates at ion energies below 50 eV, while etching occurs above that energy with an etch rate of three to seven times that in Cl. The faster etch rate in BCl was attributed to a change in the dominant ion from Cl{sup +} in Cl plasma to BCl{sup +} in BCl, which facilitated the formation of more volatile etch products and their removal. The surface chlorination (0-3 at. %) was enhanced with increasing ion energy while the amount of boron on the surface increases with decreasing ion energy, highlighting the effect of different plasma chemistries on the etch rates, etch product formation, and surface termination.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2009; 27(2):217-223. · 1.43 Impact Factor
  • Ryan M. Martin, Jane P. Chang
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    ABSTRACT: A generalized etch rate model was formulated to describe metal oxide etching in complex plasma chemistries, based on the understanding gained from detailed plasma characterization and experimental investigation into the metal oxide etching mechanisms. Using a surface site balance-based approach, the correct etch rate dependencies on neutral-to-ion flux ratio, ion energy, competing deposition and etching reaction pathways, and film properties were successfully incorporated into the model. The applicability of the model was assessed by fitting to experimental etch rate data in both Cl and BCl chemistries. Plasma gas phase analysis as well as etch and deposition rate measurements were used to calculate initial values and appropriate ranges for model parameter variation. Physically meaningful parameter values were extracted from the modeling fitting to the experimental data, thereby demonstrating the applicability of this model in assessing the plasma etching of other complex materials systems.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2009; 27(2):224-229. · 1.43 Impact Factor

Publication Stats

752 Citations
162.34 Total Impact Points

Institutions

  • 2000–2012
    • University of California, Los Angeles
      • Department of Chemical and Biomolecular Engineering
      Los Angeles, CA, United States
  • 2005–2008
    • CSU Mentor
      Long Beach, California, United States
  • 1997–1998
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States