Silicon nanowires (SiNWs) were fabricated by the electroless etching of an n-type Si (100) wafer in HF/AgNO. Vertically aligned and high-density SiNWs are formed on the Si substrates. Various shapes of SiNWs are observed, including round, rectangular, and triangular. The recorded maximum reflectance of the SiNWs is approximately 19.2%, which is much lower than that of the Si substrate (65.1%). The minimum reflectance of the SiNWs is approximately 3.5% in the near UV region and 9.8% in the visible to near IR regions. The calculated band gap energy of the SiNWs is found to be slightly higher than that of the Si substrate. The I-V characteristics of a freestanding SiNW show a linear ohmic behavior for a forward bias up to 2.0 V. The average resistivity of a SiNW is approximately 33.94 Ω cm.