TEM study of CdS nanocrystals formed in SiO2 by ion implantation

1996 ◽  
Vol 54 ◽  
pp. 236-237
Author(s):  
Jane G. Zhu ◽  
C. W. White ◽  
J. D. Budai ◽  
S. P. Withrow
Keyword(s):  
Ion Implantation ◽  
Electronic Device ◽  
Semiconductor Nanocrystals ◽  
Optical Nonlinearity ◽  
Silicon Substrates ◽  
Cds Nanocrystals ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Device Applications ◽  
Ion Profiles

Quantum confinement effects and enhanced optical nonlinearity are expected from II-VI semiconductor nanocrystals, which are important for novel opto-electronic device applications. The ion implantation method has been used in our study to form CdS nanocrystals inside amorphous SiO2. The CdS nanocrystals were studied by transmission electron microscopy (TEM).The samples were implanted (at room temperature) with equal doses (1×1017 ions/cm2) of Cd and S into a SiO2 layer on (100) silicon substrates and then annealed under Ar + 4%H2 ambient at 800°C and 1000°C for 1 h. Implant energies were chosen to overlap the Cd and S ion profiles in the middle of the oxide layer. CdS precipitates are formed during the thermal annealing.The effect of annealing temperatures on the nanocrystals size distributions are revealed in Figs. 1 and 2. The sizes of CdS nanocrystals are in the range of 2 - 11 nm for the sample annealed at 800°C, and in the range of a few to 16 nm for the sample annealed at 1000°C.

Microstructure and Size Distribution of Compound Semiconductor Nanocrystals Synthesized by Ion Implantation

1998 ◽  
Vol 536 ◽  
Author(s):  
A. Meldrum ◽  
S. P. Withrow ◽  
R. A. Zuhr ◽  
C. W. White ◽  
L. A. Boatnerl ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Semiconductor Nanocrystals ◽  
Compound Semiconductor ◽  
Fused Silica ◽  
Silica Matrix ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Host Materials ◽  
Device Applications ◽  
Versatile Technique

AbstractIon implantation is a versatile technique by which compound semiconductor nanocrystals may be synthesized in a wide variety of host materials. The component elements that form the compound of interest are implanted sequentially into the host, and nanocrystalline precipitates then form during thermal annealing. Using this technique, we have synthesized compound semiconductor nanocrystal precipitates of ZnS, CdS, PbS, and CdSe in a fused silica matrix. The resulting microstructures and size distributions were investigated by cross-sectional transmission electron microscopy. Several unusual microstructures were observed, including a band of relatively large nanocrystals at the end of the implant profile for ZnS and CdSe, polycrystalline agglomerates of a new phase such as γ-Zn 2SiO4, and the formation of central voids inside CdS nanocrystals. While each of these microstructures is of fundamental interest, such structures are generally not desirable for potential device applications for which a uniform, monodispersed array of nanocrystals is required. Methods were investigated by which these unusual microstructures could be eliminated.

Microstructure of GaAs nanocrystals formed inside single crystalline silicon

1996 ◽  
Vol 54 ◽  
pp. 968-969
Author(s):  
Jane G. Zhu ◽  
C. W. White ◽  
J. D. Budai ◽  
M. J. Yacaman ◽  
G. Mondragon
Keyword(s):  
Electronic Device ◽  
Crystalline Silicon ◽  
Semiconductor Nanocrystals ◽  
Implantation Technique ◽  
Single Crystalline Silicon ◽  
Semiconductor Technology ◽  
Cross Sectional ◽  
Si Substrates ◽  
Transmission Electron ◽  
Device Applications

Semiconductor nanocrystals exhibit novel properties that are important for electronic and opto-electronic device applications. Many methods have been developed to synthesize semiconductor nanocrystals. Among them is the ion implantation technique, which is compatible with the semiconductor technology. It has been recently reported that the compound semiconductor GaAs can be formed inside Si by sequential implantation of Ga and As and thermal annealing.In this study, GaAs nanocrystals were formed by sequential implantation of As and Ga, with the same dose of 1 x 1017 cm-2, into (100) Si substrates at 550°C. The implantation energies were chosen so that the Ga and As ions are overlapped over a few hundred nanometers in depth. The samples were then annealed at 1000°C for 1 h in flowing Ar + 4%H2 atmosphere to form GaAs precipitates. Transmission electron microscopy (TEM) has been used to study the microstructures of these samples.The cross-sectional TEM image in Fig. 1 shows the GaAs precipitates formed inside the Si substrateimplanted with As and then Ga.

Colloidal semiconductor nanocrystals: synthesis, optical nonlinearity, and related device applications

2021 ◽  
Author(s):  
Min Li ◽  
Cong Wang ◽  
Lude Wang ◽  
Han Zhang
Keyword(s):  
Nonlinear Optical ◽  
Rapid Development ◽  
Semiconductor Nanocrystals ◽  
Optical Nonlinearity ◽  
Photonic Devices ◽  
Nlo Properties ◽  
Novel Materials ◽  
Colloidal Semiconductor Nanocrystals ◽  
Device Applications ◽  
Colloidal Semiconductor

The rapid development of photonic devices requires the exploration of novel materials with superior nonlinear optical (NLO) properties. Colloidal semiconductor nanocrystals (NCs) exhibit size-tunable exciton resonances and excellent NLO properties....

Quantitative Experimental Determination of The Effect of Dislocation - Dislocation Interactions on Strain Relaxation in Lattice Mismatched Heterostructures

1998 ◽  
Vol 535 ◽  
Author(s):  
E. A. Stach ◽  
R. Hull ◽  
R. M. Tromp ◽  
F. M. ROSS ◽  
M. C. Reuter ◽  
...  
Keyword(s):  
Electronic Device ◽  
Blocking Probability ◽  
Strain Relaxation ◽  
Interaction Force ◽  
Strained Layers ◽  
Dislocation Interaction ◽  
Transmission Electron ◽  
Dislocation Interactions ◽  
Device Applications ◽  
Gap States

AbstractWe present real time observations of the interaction of dislocations in heteroepitaxial strained layers using a specially modified ultrahigh vacuum transmission electron microscope equipped with in-situ deposition capabilities. These observations have led to delineation of the regime of epilayer thickness and composition where dislocation interactions result in blocking of the propagating threading segment. It is found that both the blocking probability as well as the magnitude of the dislocation interaction force are strongly dependent on the Burgers vectors of the dislocations involved, with the greatest effects observed when the Burgers vectors of the two dislocations are parallel with respect to each other. Frame-by-frame analysis of the motion of the dislocation threading segment during interaction is used to extract the magnitude of the interaction stresses as a function of both the level of heteroepitaxial strain and the dislocation geometry. Finally, by continuing growth following observations of blocking during annealing, we find that blocked dislocations are likely to remain in that configuration until substantial additional heteroepitaxial stresses are incorporated into the layer. These results have direct relevance to the successful integration of strained layer heterostructures into electronic device applications. This is because blocked threading segments result in the introduction of undesired band gap states, enhance impurity diffusion, modify surface morphology and act to limit the dislocation density reductions achievable in graded buffer structures.

Semiconductor Nanocrystals formed in SiO2 by Ion Implantation

1994 ◽  
Vol 358 ◽  
Author(s):  
Jane G. Zhu ◽  
C. W. White ◽  
J. D. Budai ◽  
S. P. Withrow ◽  
Y. Chen
Keyword(s):  
Ion Implantation ◽  
Annealing Temperature ◽  
Semiconductor Nanocrystals ◽  
Spherical Shape ◽  
Group Iv ◽  
Semiconductor Materials ◽  
Size Distributions ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Subsequent Thermal Annealing

ABSTRACTNanocrystals of group IV (Si, Ge and SiGe), III-V (GaAs), and II-VI (CdSe) semiconductor materials have been fabricated inside SiO2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystalline semiconductor materials has been studied by transmission electron microscopy (TEM). The nanocrystals form in near-spherical shape with random crystal orientations in amorphous SiO2 Extensive studies on the nanocrystal size distributions have been carried out for the Ge nanocrystals by changing the implantation doses and the annealing temperatures. Remarkable roughening of the nanocrystals occurs when the annealing temperature is raised over the melting temperature of the implanted semiconductor material. Strong red photoluminescence peaked around 1.67 eV has been achieved in samples with Si nanocrystals in SiO2.

Luminescent Nanometer-Sized Si Crystals Formed in an amorphous Silicon Dioxide Matrk by Ion Implantation and Annealing

1995 ◽  
Vol 388 ◽  
Author(s):  
T.S. Iwayama ◽  
Y. Terao ◽  
A. Kamiya ◽  
M. Takeda ◽  
S. Nakao ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Annealing Time ◽  
Band Gap Energy ◽  
Electron Hole ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Average Size ◽  
Si Ion Implantation ◽  
Hole Recombination

AbstractSi ion implantation followed by thermal annealing has been used to synthesize luminescent nanometer-sized Si crystals in an amorphous Si02 matrix. Transmission electron microscopy indicates the formation of Si nanocrystals by annealing at 1100 °C, and the growth in average size of Si nanocrystals with increasing annealing time. the shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time, while the excitation spectrum of photoluminescence increases as the photon energy increases and its shape depends on annealing time. the results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and Si02.

Electronic Cone Illumination with the Conventional Transmission Electron Microscope

1977 ◽  
Vol 35 ◽  
pp. 72-73
Author(s):  
William Krakow
Keyword(s):  
Electronic Device ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Hollow Cone ◽  
Transmission Electron ◽  
Lissajous Figures ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Diffraction Patterns ◽  
Transmission Microscope

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates

1975 ◽  
Vol 33 ◽  
pp. 96-97
Author(s):  
R. W. Ditchfield ◽  
A. G. Cullis
Keyword(s):  
Epitaxial Growth ◽  
Electron Energy ◽  
Silicon Substrates ◽  
Secondary Phases ◽  
Si Substrates ◽  
Transmission Electron ◽  
Layer Structures ◽  
Si Films ◽  
Electron Energy Loss ◽  
Growth Centres

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.

Interlayer mixing in GaAs/AlxGa1-xAs heterostructures as a result of Se+ ion implantation

1988 ◽  
Vol 46 ◽  
pp. 908-909
Author(s):  
E.G. Bithell ◽  
W.M. Stobbs
Keyword(s):  
Ion Implantation ◽  
Diffusion Coefficients ◽  
Dark Field ◽  
Atomic Mass ◽  
Composition Profile ◽  
Semiconductor Heterostructures ◽  
Transmission Electron ◽  
Microscope Images ◽  
Damage Process ◽  
Electron Energy Loss

It is well known that the microstructural consequences of the ion implantation of semiconductor heterostructures can be severe: amorphisation of the damaged region is possible, and layer intermixing can result both from the original damage process and from the enhancement of the diffusion coefficients for the constituents of the original composition profile. A very large number of variables are involved (the atomic mass of the target, the mass and energy of the implant species, the flux and the total dose, the substrate temperature etc.) so that experimental data are needed despite the existence of relatively well developed models for the implantation process. A major difficulty is that conventional techniques (e.g. electron energy loss spectroscopy) have inadequate resolution for the quantification of any changes in the composition profile of fine scale multilayers. However we have demonstrated that the measurement of 002 dark field intensities in transmission electron microscope images of GaAs / AlxGa1_xAs heterostructures can allow the measurement of the local Al / Ga ratio.

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