Solid State

With which one of the following elements silicon should be doped so as to give p-type of semiconductor?

1. Selenium
2. Boron
3. Germanium
4. Arsenic

If a stands for the edge length of the cubic systems: simple cubic, body centred cubic and face centred cubic, then the ratio of radii of the spheres in these systems will be respectively

1. 12a : 32a : 22a
2. 1a : 3a : 2a
3. 12a : 34a : 12 2a
4. 12a : 3a : 1 2a

For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct?

1. a b c and = = = 90
2. a = b = c and = 90
3. a = b = c and = = = 90
4. a b c and and = 90

The fraction of total volume occupied by the atoms present in a simple cubic unit cell is

1. 3 2
2. 4 2
3. 4
4. 6

If NaCl is doped with 10-4 mol% of SrCl2, the concentration of cation vacancies will be (NA = 6.02 1023 mol-1)

1. 6.02 1016 mol-1
2. 6.02 1017 mol-1
3. 6.02 1014 mol-1
4. 6.02 1015 mol-1

The appearance of colour in solid alkali metal halides is generally due to

1. interstitial positions
2. F-centres
3. Schottky defect
4. Frenkel defect

CsBr crystallises in a body centered cubic lattice. The unit cell length is 436.6 pm. Given that the atomic mass of Cs = 133 and that of Br = 80 amu and Avogadro number being 6.02 1023 mol-1, the density of CsBr is

1. 4.25 g/cm3
2. 42.5 g/cm3
3. 0.425 g/cm3
4. 8.25 g/cm3

Copper has face centered cubic (fcc) lattice with interatomic spacing equal to 2.54 A. The value of lattice constant for this lattice is

1. 2.54 A
2. 3.59 A
3. 1.27 A
4. 5.08 A

In a face-centered cubic lattice, a unit cell is shared equally by how many unit cells?

1. 2
2. 4
3. 6
4. 8

A compound formed by elements X and Y crystallizes in a cubic structure in which the X atoms are at the corners of a cube and the Y atoms are at the face-centers. The formula of the compound is :-

1. XY3
2. X3Y
3. XY
4. XY2