Dong Su Lee

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We address the quantum Hall behavior in twisted bilayer graphene transferred from the C face of SiC. The measured Hall conductivity exhibits the same plateau values as for a commensurate Bernal bilayer. This implies that the eightfold degeneracy of the zero energy mode is topologically protected despite rotational disorder as recently predicted. In(More)
Chemically modified graphene was synthesized by chemical vapour deposition (CVD) with ammonia gas introduced during the CVD process. The use of two different metal catalyst films [nickel (Ni) or copper (Cu)] results in distinctly different forms of structural defects in the honeycomb lattice of graphene under identical synthesis conditions. The Ni catalyst(More)
New approaches are developed to use peak penetration-induced pore pressure magnitudes to index profiles of in situ permeability. These methods potentially enable permeability profiles to be determined from continuous sounding by cone penetrometers, and from freefalling marine penetrometers that self-embed into seafloor sediments. Solutions are developed for(More)
The ultraviolet ͑UV͒ photoluminescence ͑PL͒ properties of Tm-doped Al x Ga 1−x N ͑0.39Յ x Յ 1͒ alloys grown by solid-source molecular beam epitaxy were probed using above-bandgap excitation from a laser source at 197 nm. The PL spectra show dominant UV emissions at 298 and 358 nm only for samples with x = 1 and 0.81. Temperature dependence of the PL(More)
Noncontact modulation calorimetry using electromagnetic heating and radiative heat loss under ultrahigh-vacuum conditions has been applied to levitated solid, liquid, and metastable liquid samples. This experiment requires a reduced gravity environment over an extended period of time and allows the measurement of several thermophysical properties, such as(More)
A novel and facile synthetic method for h-BN films from borazine oligomer (B3N3H4)x precursors has been developed. This method only includes spin-coating of borazine oligomer onto nickel catalysts and a subsequent annealing step. Large areal and highly crystalline h-BN films were obtained. The stoichiometric B/N ratio of borazine oligomer precursor was(More)
Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states(More)
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