The band-edge excitons observed in few-layer NiPS3

Band-edge excitons of few-layer nickel phosphorous trisulfide (NiPS3) are characterized via micro-thermal-modulated reflectance (μTR) measurements from 10 to 300 K. Prominent μTR features of the A exciton series and B are simultaneously detected near the band edge of NiPS3. The A exciton series contains two sharp A1 and A2 levels and one threshold-energy-related transition (direct gap, E∞), which are simultaneously detected at the lower energy side of NiPS3. In addition, one broadened B feature is present at the higher energy side of few-layer NiPS3. The A series excitons may correlate with majorly d-to-d transition in the Rydberg series with threshold energy of E∞ ≅ 1.511 eV at 10 K. The binding energy of A1 is about 36 meV, and the transition energy is A1 ≅ 1.366 eV at 300 K. The transition energy of B measured by μTR is about 1.894 eV at 10 K. The excitonic series A may directly transit from the top of valence band to the conduction band of NiPS3, while the B feature might originate from the spin-split-off valence band to the conduction band edge. The direct optical gap of NiPS3 is ~1.402 eV at 300 K, which is confirmed by μTR and transmittance experiments.

Thriving in a Net-Zero Office—Looking Beyond Energy to Create Quality in Human Work Spaces

Better energy performance (i.e., net-zero or carbon neutral) is not the only dimension where better buildings quality is needed. It may just be the easiest one to measure. Three interrelated dimensions—productivity and its cousins, health and comfort—are the next in line. The building of the future will bring far more intelligence—and quality—to those dimensions, in order to compete for occupants and potentially to help to pay for the efficiency needed on the energy side. The economics of productivity and health gains or losses can dwarf—in upside or downside—what happens on the energy front. This paper describes specific drivers of health and productivity and comfort, and discusses their use in the design and occupancy of Rocky Mountain Institute’s (RMI’s) new net-zero building in Colorado as a test case to look at design and occupant engagement issues. The paper details the most important design and behavior tradeoffs encountered, and discusses paths to effectively resolving them and accelerating change.

Bandgap Energies of Cubic AlxGa1−xNyAs1−y Calculated by Means of the Dielectric Method

ABSTRACTBandgap energies of the group III-V quaternary alloy semiconductor, cubic AlxGa1−xNyAs1−y, were calculated by means of the dielectric method. While only GaN and GaAs are considered to be direct transition type among the four constituent binary compounds of this quaternary alloy system, the calculation results show that the bandgap energy range covered in the direct transition regime of this alloy system was further extended to the higher energy side of GaN as well as to the lower energy sides of GaAs. The extension to the higher energy side was attributed to the larger direct bandgap of AlN. On the other hand, the extension to the lower energy side was caused by the large bowing in the bandgap energy between group III nitrides and arsenides. Calculations under lattice matching to Si and GaAs are also presented.