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Papers by javier viejo
MRS Proceedings, 1996
Quantum dot composite films, consisting of II-VI nanocrystals imbedded in a ZnS matrix, are candi... more Quantum dot composite films, consisting of II-VI nanocrystals imbedded in a ZnS matrix, are candidate phosphor materials for electroluminescent flat panel displays. The optical properties of such composites can be tailored across the visible spectral region by selecting the composition and size of the nanocrystals. We present combined solution chemistry and electrospray organometallic chemical vapor deposition (ES-OMCVD) methods for realizing such composites. Size selected, CdSe quantum dots with an overlayer of ZnS are synthesized in solution. This surface derivatization produces a large enhancement of the photoluminescence efficiency. The quantum dot composites are subsequently formed by introducing the quantum dot solution by electrospray into an OMCVD ZnS thin film process. Photoluminescence and cathodoluminescence properties of the quantum dot composites are reported.
Organic Light-Emitting Materials and Devices II, 1998
ABSTRACT
MRS Proceedings, 1996
We report cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe ... more We report cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals of 33 and 42 Å diameter imbedded in a ZnS matrix. The thin film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and on the voltage and current density applied. Electron beam irradiation caused a decrease of the luminescence which may be explained by electron ionization of the quantum dots. Quenching of the cathodoluminescence at low temperatures is attributed to a more efficient trapping of the ionized electrons in deep traps inside the ZnS matrix.
The Journal of Physical Chemistry B, 1997
Most Read articles are updated on a monthly basis and available as 1 month and 12 month lists. Be... more Most Read articles are updated on a monthly basis and available as 1 month and 12 month lists. Below are the the journal's Top 20 most downloaded articles over the last 12 months. Choose a timeframe: 1 Month 12 months List of Issues
Journal of Crystal Growth, 1998
A modified organometallic chemical vapor deposition technique is used to incorporate luminescing ... more A modified organometallic chemical vapor deposition technique is used to incorporate luminescing II-VI nanocrystals (NCs) into ZnS thin films. The NCs are synthesized in organic solution and consist of a CdSe core and ZnS shell. The ZnS matrix is deposited by OMCVD from diethyl zinc and hydrogen sulfide while the NCs are delivered to the film surface via electrospray. Varying the size of the CdSe NC core enables tunable emission from the blue to the red. The ZnS shell provides electronic and chemical passivation of the CdSe core improving its luminescence and thermal stability. The thin films exhibit room temperature photoluminescence (PL) and cathodoluminescence (CL) dominated by emission from the NCs. PL quantum efficiencies greater than 10% have been achieved. The dependence of thin film luminescence and microstructure on deposition temperature is studied using optical photoluminescence and X-ray diffraction. Particular emphasis is placed on the relationship between the host ZnS structure and the optical properties of the NC-ZnS composite thin film.
Applied Physics Letters, 1997
We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS... more We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window ͑470-650 nm͒ by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied.
MRS Proceedings, 1996
Quantum dot composite films, consisting of II-VI nanocrystals imbedded in a ZnS matrix, are candi... more Quantum dot composite films, consisting of II-VI nanocrystals imbedded in a ZnS matrix, are candidate phosphor materials for electroluminescent flat panel displays. The optical properties of such composites can be tailored across the visible spectral region by selecting the composition and size of the nanocrystals. We present combined solution chemistry and electrospray organometallic chemical vapor deposition (ES-OMCVD) methods for realizing such composites. Size selected, CdSe quantum dots with an overlayer of ZnS are synthesized in solution. This surface derivatization produces a large enhancement of the photoluminescence efficiency. The quantum dot composites are subsequently formed by introducing the quantum dot solution by electrospray into an OMCVD ZnS thin film process. Photoluminescence and cathodoluminescence properties of the quantum dot composites are reported.
Organic Light-Emitting Materials and Devices II, 1998
ABSTRACT
MRS Proceedings, 1996
We report cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe ... more We report cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals of 33 and 42 Å diameter imbedded in a ZnS matrix. The thin film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and on the voltage and current density applied. Electron beam irradiation caused a decrease of the luminescence which may be explained by electron ionization of the quantum dots. Quenching of the cathodoluminescence at low temperatures is attributed to a more efficient trapping of the ionized electrons in deep traps inside the ZnS matrix.
The Journal of Physical Chemistry B, 1997
Most Read articles are updated on a monthly basis and available as 1 month and 12 month lists. Be... more Most Read articles are updated on a monthly basis and available as 1 month and 12 month lists. Below are the the journal's Top 20 most downloaded articles over the last 12 months. Choose a timeframe: 1 Month 12 months List of Issues
Journal of Crystal Growth, 1998
A modified organometallic chemical vapor deposition technique is used to incorporate luminescing ... more A modified organometallic chemical vapor deposition technique is used to incorporate luminescing II-VI nanocrystals (NCs) into ZnS thin films. The NCs are synthesized in organic solution and consist of a CdSe core and ZnS shell. The ZnS matrix is deposited by OMCVD from diethyl zinc and hydrogen sulfide while the NCs are delivered to the film surface via electrospray. Varying the size of the CdSe NC core enables tunable emission from the blue to the red. The ZnS shell provides electronic and chemical passivation of the CdSe core improving its luminescence and thermal stability. The thin films exhibit room temperature photoluminescence (PL) and cathodoluminescence (CL) dominated by emission from the NCs. PL quantum efficiencies greater than 10% have been achieved. The dependence of thin film luminescence and microstructure on deposition temperature is studied using optical photoluminescence and X-ray diffraction. Particular emphasis is placed on the relationship between the host ZnS structure and the optical properties of the NC-ZnS composite thin film.
Applied Physics Letters, 1997
We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS... more We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window ͑470-650 nm͒ by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied.