Controlling the Microstructure and Magnetic Properties of Ferromagnetic Nanocrystals Produced by Ion Implantation

2001 ◽  
Vol 703 ◽  
Author(s):  
K.S. Beaty ◽  
A. Meldrum ◽  
J.P. Franck ◽  
K. Sorge ◽  
J. R. Thompson ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Ion Implantation ◽  
Magnetic Circular Dichroism ◽  
Magnetic Hysteresis ◽  
Near Surface ◽  
Magnetic Elements ◽  
Transmission Electron ◽  
Wide Range ◽  
Co Nanoparticles

ABSTRACTIon implantation coupled with annealing is a versatile and flexible approach to creating ferromagnetic near-surface nanocomposites that represent a wide range of particle/host combinations. We have used ion implantation and thermal processing to create a layer of Co nanoparticles in a sapphire host that was subsequently irradiated with Xe, Pt, or Pb in order to systematically modify the magnetic properties of the composite. Transmission electron microscopy (reported in an accompanying paper in this volume) was used to carry out a detailed characterization of the microstructure of the resulting near-surface composites whose magnetic properties were determined using SQUID magnetometry or magnetic circular dichroism. These composites exhibit magnetic hysteresis with coercivities ranging from near zero (i.e., superparamagnetism) up to 1.2 kG - depending on the composition and microstructure. We also present the results of preliminary experiments in which we attempt to control the spatial distribution of magnetic elements within ion-implanted ferromagnetic nanocomposites. The results demonstrate methods for tailoring the magnetic properties of nanocomposites produced by ion implantation for specific applications.

The Formation of High-Coercivity, Oriented, Nanophase Cobalt Precipitates in Al2O3 Single Crystals by Ion Implantation

1999 ◽  
Vol 581 ◽  
Author(s):  
S. Honda ◽  
F. A. Modine ◽  
T. E. Haynes ◽  
A. Meldrum ◽  
J. D. Budai ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Ion Implantation ◽  
Single Crystals ◽  
Data Storage ◽  
Magnetic Circular Dichroism ◽  
Surface Region ◽  
Magnetic Data ◽  
High Coercivity ◽  
Saturation Field ◽  
Near Surface

ABSTRACTIon-implantation and thermal-processing methods have been used to form nanophase magnetic precipitates of metallic cobalt that are embedded in the near-surface region of single crystals of Al2O3. The Co precipitates are isolated, single-crystal particles that are crystallographically oriented with respect to the host Al2O3 lattice. Embedded nanophase Co precipitates were formed by the implantation of Co+ at an energy of 140 keV and a dose of 8 × 1016 ions/cm2 followed by annealing in a reducing atmosphere. The implanted/annealed Co depth profile, particle size distributions and shapes, and the orientational relationship between the nanophase precipitates and the host crystal lattice were determined using RBS/channeling, transmission electron microscopy, and x-ray diffraction. Magneto-optical effects arising from Co precipitates formed in the near-surface region of Al2O3 were observed and characterized using magnetic circular dichroism. Magnetic properties of the Co-particle/host nanocomposites were investigated in the temperature range of 77 to 295 K in applied fields of up to 10 kG using a superconducting quantum interference device (SQUID) magnetometer. Implantation of the Co particles by Pt or Xe ions produced a large anisotropic increase in their coercivity. Accordingly, these magnetic nanoparticle systems may be of interest for magnetic data storage applications. Details of the magnetic properties of the Co/Al2O3 nanocomposites including their retentivity, coercivity, saturation field, and magnetic anisotropy are presented.

Comparison of Ion-Milling Techniques For Cross-Sectional TEM of Semiconductors

1985 ◽  
Vol 43 ◽  
pp. 166-167
Author(s):  
Julia T. Luck ◽  
C. W. Boggs ◽  
S. J. Pennycook
Keyword(s):  
Analytical Techniques ◽  
Sample Surface ◽  
Ion Milling ◽  
Cross Sectional ◽  
Reliable Technique ◽  
Near Surface ◽  
Transmission Electron ◽  
Thin Region ◽  
Transient Thermal

The use of cross-sectional Transmission Electron Microscopy (TEM) has become invaluable for the characterization of the near-surface regions of semiconductors following ion-implantation and/or transient thermal processing. A fast and reliable technique is required which produces a large thin region while preserving the original sample surface. New analytical techniques, particularly the direct imaging of dopant distributions, also require good thickness uniformity. Two methods of ion milling are commonly used, and are compared below. The older method involves milling with a single gun from each side in turn, whereas a newer method uses two guns to mill from both sides simultaneously.

Synthesis and Structural Characterization of Ferromagnetic Au/Co Nanoparticles

2014 ◽  
Vol 1708 ◽  
Author(s):  
Nabraj Bhattarai ◽  
Subarna Khanal ◽  
Daniel Bahena ◽  
Robert L. Whetten ◽  
Miguel Jose-Yacaman
Keyword(s):  
Quantum Interference ◽  
Magnetic Measurements ◽  
Ferromagnetic Behavior ◽  
Contrast Imaging ◽  
Uniform Size ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Co Nanoparticles ◽  
Z Contrast

ABSTRACTThe synthesis of bimetallic magnetic nanoparticles is very challenging because of the agglomeration and non-uniform size. In this paper, we present the synthesis of monodispersed 3-5 nm sized thiolated bimetallic alloyed Au/Co nanoparticles with decahedral and icosahedral shape, their characterization using Cs-corrected scanning transmission electron microscopy (STEM) and magnetic measurements using superconducting quantum interference device (SQUID) magnetometer. The Z-contrast imaging and energy dispersive X-ray spectroscopy (EDS) mapping showed an inhomogeneous alloying with minor segregation between Au and Co at nanoscale and the SQUID measurement exhibited the ferromagnetic behavior.

Microstructural and Compositional Characterization of SiC-On-Insulator Structures

1999 ◽  
Vol 5 (S2) ◽  
pp. 770-771
Author(s):  
Manabu Ishimaru ◽  
Robert M. Dickerson ◽  
Kurt E. Sickafus
Keyword(s):  
Ion Implantation ◽  
Integrated Circuit ◽  
High Speed ◽  
Scanning Transmission Electron Microscope ◽  
Oxygen Ions ◽  
Oxygen Ion ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Oxygen Ion Implantation

As the size of Si integrated circuit structures is continually reduced, interest in semiconductor-oninsulator (SOI) structures has heightened. SOI structures have already been developed for Si using oxygen ion implantation. However, the application of Si devices is limited due to the physical properties of Si. As an alternative to Si, SiC is a potentially important semiconductor for high-power, high-speed, and high-temperature electronic devices. Therefore, this material is a candidate for expanding the capabilities of Si-based technology. In this study, we performed oxygen ion implantation into bulk SiC to produce SiC-on-insulator structures. We examined the microstructures and compositional distributions in implanted specimens using transmission electron microscopy and a scanning transmission electron microscope equipped with an energy-dispersive X-ray spectrometer (STEM-EDX).Figures 1(a) and 2(a) show bright-field images of 6H-SiC implanted with 180 keV oxygen ions at 650 °C to fluences of 7xl017 and 1.4xl018 cm−2, respectively. Three regions with distinct image contrast are apparent in Figs. 1(a) and 2(a), as indicated by A, B, and C.

Synthesis and Characterization of Co Nanoparticles by Solventless Thermal Decomposition

2007 ◽  
Vol 119 ◽  
pp. 71-74 ◽  
Author(s):  
Yan Li ◽  
Xiao Li Zhang ◽  
Young Hwan Kim ◽  
Young Soo Kang
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Synthesis And Characterization ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Structure Of Nanoparticles ◽  
Co Nanoparticles

Co nanoparticles were synthesized via a solventless thermal decomposition of Co2+-oleate2. The crystalline structure is strongly affected by the thermal treatment of the Co nanoparticles. Further, the annealing also results in the decomposition of surfactant around Co particles. The size of nanoparticles was confirmed by transmission electron microscopy (TEM). The crystal structure of nanoparticles was characterized by X-ray diffraction pattern (XRD). The magnetic properties were characterized by vibrating sample magnetometer (VSM).

Using Ion Beams to Modify Nanocrystalline Composites: Co Nanoparticles in Sapphire

2001 ◽  
Vol 703 ◽  
Author(s):  
A. Meldrum ◽  
K.S. Beaty ◽  
M. Lam ◽  
C.W. White ◽  
R.A. Zuhr ◽  
...  
Keyword(s):  
Surface Region ◽  
Amorphous Layer ◽  
Ion Beams ◽  
Near Surface ◽  
Nanocrystalline Composites ◽  
Transmission Electron ◽  
Co Nanoparticles ◽  
20 Nm ◽  
And Control ◽  
Single Crystal Sapphire

ABSTRACTIon implantation and thermal processing were used to create a layer of Co nanoclusters embedded in the near-surface region of single-crystal sapphire. The Co nanoparticles ranged in size from 2-20 nm and were crystallographically aligned with the host sapphire. Specimens were irradiated with Xe and Pt ions, and the microstructural evolution of the nanoclusters was investigated by transmission electron microscopy. With increasing Pt or Xe ion dose, the Co nanoparticles lost their initially excellent faceting, although they remained crystalline. The host Al2O3 became amorphous and the resulting microstructure consisted of a buried amorphous layer containing the still-crystalline Co nanoparticles. EDS mapping and electron diffraction were used to determine the distribution of the implanted species, and the magnetic properties of the composite were measured with a SQUID magnetometer. The results show that ion beams can be applied to modify and control the properties of ferromagnetic nanocomposites, and, combined with lithographic techniques, will find applications in exercising fine-scale spatial control over the properties of magnetic materials.

scholarly journals Nanocrystal Formation Via Yttrium Ion Implantation into Sapphire

1995 ◽  
Vol 396 ◽  
Author(s):  
E. M. Hunt ◽  
J. M. Hampikian ◽  
D. B. Poker
Keyword(s):  
Ion Implantation ◽  
Face Centered Cubic ◽  
Near Surface ◽  
X Ray ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Face Centered ◽  
Amorphous Surface ◽  
Yttrium Ion ◽  
Nanosized Crystals

AbstractIon implantation has been used to form nanocrystals in the near surface of single crystal A12O3. The ion fluence was 5 x 1016 Y+/cm2, and the implant energies investigated were 100, 150, and 170 keV. The morphology of the implanted region was investigated using transmission electron microscopy, x-ray energy dispersive spectroscopy, Rutherford backscattering spectroscopy and ion channeling. The implantation causes the formation of an amorphous surface layer which contains spherical nanosized crystals with a diameter of ∼13 nm. The nanocrystals are randomly oriented and exhibit a face-centered cubic structure with a lattice pmeter of ∼4.1 A ± .02 A. Preliminary chemical analysis shows that these nanocrystals are rich in aluminum and yttrium and poor in oxygen relative to the amorphous matrix.

BIC Formation and Boron Diffusion in Relaxed Si0.8Ge0.2

2004 ◽  
Vol 810 ◽  
Author(s):  
R. T. Crosby ◽  
L. Radic ◽  
K. S. Jones ◽  
M. E. Law ◽  
P.E. Thompson ◽  
...  
Keyword(s):  
Surface Region ◽  
Extended Defects ◽  
Defect Structures ◽  
Boron Diffusion ◽  
Plan View ◽  
Near Surface ◽  
Transmission Electron ◽  
Secondary Ion ◽  
Ion Implanted

ABSTRACTThe relationships between Boron Interstitial Cluster (BIC) evolution and boron diffusion in relaxed Si0.8Ge0.2 have been investigated. Structures were grown by Molecular Beam Epitaxy (MBE) with surface boron wells of variant composition extending 0.25 [.proportional]m into the substrate, as well as boron marker layers positioned 0.50 [.proportional]m below the surface. The boron well concentrations are as follows: 0, 7.5×1018, 1.5×1019, and 5.0×1019 atoms/cm3. The boron marker layers are approximately 3 nm wide and have a peak concentration of 5×1018 atoms/cm3. Samples were ion implanted with 60 keV Si+ at a dose of 1×1014 atoms/cm2 and subsequently annealed at 675°C and 750°C for various times. Plan-view Transmission Electron Microscopy (PTEM) was used to monitor the agglomeration of injected silicon interstitials and the evolution of extended defects in the near surface region. Secondary Ion Mass Spectroscopy (SIMS) concentration profiles facilitated the characterization of boron diffusion behaviors during annealing. Interstitial supersaturation conditions and the resultant defect structures of ion implanted relaxed Si0.8Ge0.2 in both the presence and absence of boron have been characterized.

Development of Magneto-Optical Imaging for High-Throughput Characterization of Combinatorial Magnetic Thin Films

2003 ◽  
Vol 804 ◽  
Author(s):  
X. R. Zhao ◽  
N. Okazaki ◽  
Y. Konishi ◽  
K. Akahane ◽  
Z. Kuang ◽  
...  
Keyword(s):  
Thin Films ◽  
High Throughput ◽  
Combinatorial Library ◽  
Imaging System ◽  
Magnetic Circular Dichroism ◽  
Magnetic Hysteresis ◽  
Magnetic Thin Films ◽  
Different Temperatures ◽  
Combinatorial Technique

ABSTRACTA new magneto-optical (MO) imaging system for high-throughput characterization of combinatorial magnetic thin films has been developed. The instrument allows us to measure both Faraday rotation and ellipticity maps at various wavelengths (400 nm∼1000 nm), different magnetic fields (0∼2000 G), and different temperatures (12 K∼300 K) for wide variety of materials. We used the magnetic circular dichroism (MCD) modulation technique to map MO properties, relatively free from substrate effects. The superiority of this system is that magnetic hysteresis curves of numerous specimens with different compositions prepared by the combinatorial technique can be simultaneously measured at one sweep of magnetic field, providing an efficient characterization method for combinatorial magnetic materials. We also confirmed that the system possesses enough spatial resolution and sensitivity for detecting MO signals of individual pixels contained in a combinatorial library.

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