Joseph Luther - Academia.edu (original) (raw)
Papers by Joseph Luther
Comanche chief Katemcy is one of the unrecognized champions of the Penateka Comanches of Texas. A... more Comanche chief Katemcy is one of the unrecognized champions of the Penateka Comanches of Texas. Although a subchief under Santa Anna, it was Katemcy who first met with Meusebach in 1847 at the present-day site of Mason, Texas. It was Katemcy who made possible the celebrated treaty between the Fredericksburg Germans under the leadership of John O. Meusebach and the Penataka Comanches on the San Saba River
The journal of physical chemistry letters, Jan 5, 2015
The electronic structure and related optical properties of an emerging thin-film photovoltaic mat... more The electronic structure and related optical properties of an emerging thin-film photovoltaic material CH3NH3PbBr3 are studied. A block-shaped α-phase CH3NH3PbBr3 single crystal with the natural ⟨100⟩ surface is synthesized solvothermally. The room-temperature dielectric function ε = ε1 + iε2 spectrum of CH3NH3PbBr3 is determined by spectroscopic ellipsometry from 0.73 to 6.45 eV. Data are modeled with a series of Tauc-Lorentz oscillators, which show the absorption edge with a strong excitonic transition at ∼2.3 eV and several above-bandgap optical structures associated with the electronic interband transitions. The energy band structure and ε data of CH3NH3PbBr3 for the CH3NH3(+) molecules oriented in the ⟨111⟩ and ⟨100⟩ directions are obtained from first-principles calculations. The overall shape of ε data shows a qualitatively good agreement with experimental results. Electronic origins of major optical structures are discussed.
Nano Letters, Feb 4, 2013
The electrostatic potential distribution across single, isolated, colloidal heterostructured nano... more The electrostatic potential distribution across single, isolated, colloidal heterostructured nanorods (NRs) with component materials expected to form a p-n junction within each NR has been measured using scanning Kelvin probe microscopy (SKPM). We compare CdS to bicomponent CdS-CdSe, CdS-PbSe, and CdS-PbS NRs prepared via different synthetic approaches to corroborate the SKPM assignments. The CdS-PbS NRs show a sharp contrast in measured potential across the material interface. We find the measured built-in potential within an individual NR to be attenuated by long-range electrostatic forces between the sample substrate, cantilever, and the measuring tip. Surface potential images were deconvoluted to yield built-in potentials ranging from 375 to 510 meV in the heterostructured NRs. We deduce the overall built-in potential as well as the charge distribution across each segment of the heterostructured NRs by combining SKPM data with simulations of the system.
The Journal of Physical Chemistry Letters, 2015
We report on photoconductivity of films of CdTe nanocrystals (NCs) using time-resolved microwave ... more We report on photoconductivity of films of CdTe nanocrystals (NCs) using time-resolved microwave photoconductivity (TRMC). Spherical and tetrapodal CdTe NCs with tunable size-dependent properties are studied as a function of surface ligand (including inorganic molecular chalcogenide species) and annealing temperature. Relatively high carrier mobility is measured for films of sintered tetrapod NCs (4 cm2/Vs). Our TRMC findings show that Te2- capped CdTe NCs show a marked improvement carrier mobility (11 cm2/Vs) indicating that NC surface termination can be altered to play a crucial role in charge-carrier mobility even after the NC solids are sintered into bulk films.
Comanche chief Katemcy is one of the unrecognized champions of the Penateka Comanches of Texas. A... more Comanche chief Katemcy is one of the unrecognized champions of the Penateka Comanches of Texas. Although a subchief under Santa Anna, it was Katemcy who first met with Meusebach in 1847 at the present-day site of Mason, Texas. It was Katemcy who made possible the celebrated treaty between the Fredericksburg Germans under the leadership of John O. Meusebach and the Penataka Comanches on the San Saba River
The journal of physical chemistry letters, Jan 5, 2015
The electronic structure and related optical properties of an emerging thin-film photovoltaic mat... more The electronic structure and related optical properties of an emerging thin-film photovoltaic material CH3NH3PbBr3 are studied. A block-shaped α-phase CH3NH3PbBr3 single crystal with the natural ⟨100⟩ surface is synthesized solvothermally. The room-temperature dielectric function ε = ε1 + iε2 spectrum of CH3NH3PbBr3 is determined by spectroscopic ellipsometry from 0.73 to 6.45 eV. Data are modeled with a series of Tauc-Lorentz oscillators, which show the absorption edge with a strong excitonic transition at ∼2.3 eV and several above-bandgap optical structures associated with the electronic interband transitions. The energy band structure and ε data of CH3NH3PbBr3 for the CH3NH3(+) molecules oriented in the ⟨111⟩ and ⟨100⟩ directions are obtained from first-principles calculations. The overall shape of ε data shows a qualitatively good agreement with experimental results. Electronic origins of major optical structures are discussed.
Nano Letters, Feb 4, 2013
The electrostatic potential distribution across single, isolated, colloidal heterostructured nano... more The electrostatic potential distribution across single, isolated, colloidal heterostructured nanorods (NRs) with component materials expected to form a p-n junction within each NR has been measured using scanning Kelvin probe microscopy (SKPM). We compare CdS to bicomponent CdS-CdSe, CdS-PbSe, and CdS-PbS NRs prepared via different synthetic approaches to corroborate the SKPM assignments. The CdS-PbS NRs show a sharp contrast in measured potential across the material interface. We find the measured built-in potential within an individual NR to be attenuated by long-range electrostatic forces between the sample substrate, cantilever, and the measuring tip. Surface potential images were deconvoluted to yield built-in potentials ranging from 375 to 510 meV in the heterostructured NRs. We deduce the overall built-in potential as well as the charge distribution across each segment of the heterostructured NRs by combining SKPM data with simulations of the system.
The Journal of Physical Chemistry Letters, 2015
We report on photoconductivity of films of CdTe nanocrystals (NCs) using time-resolved microwave ... more We report on photoconductivity of films of CdTe nanocrystals (NCs) using time-resolved microwave photoconductivity (TRMC). Spherical and tetrapodal CdTe NCs with tunable size-dependent properties are studied as a function of surface ligand (including inorganic molecular chalcogenide species) and annealing temperature. Relatively high carrier mobility is measured for films of sintered tetrapod NCs (4 cm2/Vs). Our TRMC findings show that Te2- capped CdTe NCs show a marked improvement carrier mobility (11 cm2/Vs) indicating that NC surface termination can be altered to play a crucial role in charge-carrier mobility even after the NC solids are sintered into bulk films.
In 1859, anyone could travel from San Antonio to Fredericksburg, via Bandera and Kerrville thanks... more In 1859, anyone could travel from San Antonio to Fredericksburg, via Bandera and Kerrville thanks to G. P. Phillips. Phillips ran a small store in 1859 at the corner of today’s Jefferson and Earl Garrett streets, now the site of Grimes Funeral Home. Phillips operated a mail line from San Antonio to Kerrville and Fredericksburg. Newspaper advertisements say that stagecoaches ran weekly, leaving San Antonio every Monday at 5 a.m., with overnight stops at Bandera and Kerrville. Fare from San Antonio to Bandera was 4.75;toCampVerde4.75; to Camp Verde 4.75;toCampVerde6; to Kerrville 7;andthroughtoFredericksburg7; and through to Fredericksburg 7;andthroughtoFredericksburg9.50.
Second Lieutenant Richard Irving Dodge, an 1848 West Point graduate assigned to the Eighth Infant... more Second Lieutenant Richard Irving Dodge, an 1848 West Point graduate assigned to the Eighth Infantry, was stationed at the Fort Martin Scott in April 1851. That came at a time when the post and the nearby community amounted to the last vestiges of civilization for westbound travelers. Beyond Fredericksburg lay only wild, open country and hostile Indians.
