The construction of a unit and workbook of exercises for the slow learner to develop comprehension and increase study skills for use in the teaching of an American history unit on the westward movement in the United States on a sixth grade level.

Thesis (Ed.M.)--Boston University N.B.:pages missing: 170, 171, 173 from original cop

Gate Voltage Controllable Non-Equilibrium and Non-Ohmic Behavior in Suspended Carbon Nanotubes

In this work, we measure the electrical conductance and temperature of individual, suspended quasi-metallic single-walled carbon nanotubes under high voltage biases using Raman spectroscopy, while varying the doping conditions with an applied gate voltage. By applying a gate voltage, the high-bias conductance can be switched dramatically between linear (Ohmic) behavior and nonlinear behavior exhibiting negative differential conductance (NDC). Phonon populations are observed to be in thermal equilibrium under Ohmic conditions but switch to nonequilibrium under NDC conditions. A typical Landauer transport model assuming zero bandgap is found to be inadequate to describe the experimental data. A more detailed model is presented, which incorporates the doping dependence in order to fit this data

Harvesting Planck radiation for free-space optical communications in the LWIR band

We demonstrate a free-space optical communication link with an optical transmitter that harvests naturally occurring Planck radiation from a warm body and modulates the emitted intensity. The transmitter exploits an electro-thermo-optic effect in a multilayer graphene device that electrically controls the surface emissivity of the device resulting in control of the intensity of the emitted Planck radiation. We design an amplitude-modulated optical communication scheme and provide a link budget for communications data rate and range based on our experimental electro-optic characterization of the transmitter. Finally, we present an experimental demonstration achieving error-free communications at 100 bits per second over laboratory scales

Probing NV and SiV charge state dynamics using high-voltage nanosecond pulse and photoluminescence spectral analysis

Nitrogen-vacancy (NV) and silicon-vacancy (SiV) color defects in diamond are promising systems for applications in quantum technology. The NV and SiV centers have multiple charge states, and their charge states have different electronic, optical and spin properties. For the NV centers, most investigations for quantum sensing applications are targeted on the negatively charged NV (NV$^{-}$), and it is important for the NV centers to be in the NV$^{-}$ state. However, it is known that the NV centers are converted to the neutrally charged state (NV$^{0}$) under laser excitation. An energetically favorable charge state for the NV and SiV centers depends on their local environments. It is essential to understand and control the charge state dynamics for their quantum applications. In this work, we discuss the charge state dynamics of NV and SiV centers under high-voltage nanosecond pulse discharges. The NV and SiV centers coexist in the diamond crystal. The high-voltage pulses enable manipulating the charge states efficiently. These voltage-induced changes in charge states are probed by their photoluminescence spectral analysis. The analysis result from the present experiment shows that the high-voltage nanosecond pulses cause shifts of the chemical potential and can convert the charge states of NV and SiV centers with the transition rates of $\sim$ MHz. This result also indicates that the major population of the SiV centers in the sample is the doubly negatively charged state (SiV$^{2-}$), which is often overlooked because of its non-fluorescent and non-magnetic nature. This demonstration paves a path for a method of rapid manipulation of the NV and SiV charge states in the future.Comment: 14 pages, 4 figure

Intrinsic Optical Transition Energies in Carbon Nanotubes

Intrinsic optical transition energies for isolated and individual single wall carbon nanotubes grown over trenches are measured using tunable resonant Raman scattering. Previously measured E22_S optical transitions from nanotubes in surfactants are blue shifted 70-90 meV with respect to our measurements of nanotubes in air. This large shift in the exciton energy is attributed to a larger change of the exciton binding energy than the band-gap renormalization as the surrounding dielectric constant increases.Comment: Due to a mistake, a different paper was submitted as "revised v2". This is a re-submission of the origional version in order to correct the mistak

Spatially-Resolved Temperature Measurements of Electrically-Heated Carbon Nanotubes

Spatially-resolved Raman spectra of individual pristine suspended carbon nanotubes are observed under electrical heating. The Raman G+ and G- bands show unequal temperature profiles. The preferential heating is more pronounced in short nanotubes (2 um) than in long nanotubes (5 um). These results are understood in terms of the decay and thermalization of non-equilibrium phonons, revealing the mechanism of thermal transport in these devices. The measurements also enable a direct estimate of thermal contact resistances and the spatial variation of thermal conductivity.Comment: To appear in Phys. Rev. Let