New York City gentrification, and new residents, both American transplants and new immigrants from Asia and Latin America. Important new sectors, such as Silicon Alley, emerged in the city's economy. New York's population reached all-time highs in the 2000 Census and then again in the 2010 Census. The city and surrounding area suffered the bulk of the economic damage and largest loss of human life in the aftermath of the September 11, 2001 attacks when 10 of the 19 terrorists associated with Al-Qaeda piloted American Airlines Flight 11 into the North Tower of the World Trade Center and United Airlines Flight 175 into
Polycrystalline silicon grain boundaries, see figure 1. The resistivity, mobility, and free-carrier concentration in monocrystalline silicon vary with doping concentration of the single crystal silicon. Whereas the doping of polycrystalline silicon does have an effect on the resistivity, mobility, and free-carrier concentration, these properties strongly depend on the polycrystalline grain size, which is a physical parameter that the material scientist can manipulate. Through the methods of crystallization to form polycrystalline silicon, an engineer can control the size of the polycrystalline grains which will vary the physical properties of the material. The use of polycrystalline silicon in the production of solar cells requires