Barrier for doped molybdenum targets

1. A sputtering target, comprising:

a sputtering layer comprising a first material which comprises an alkali containing transition metal; and

a support structure comprising a second material;

wherein:

the sputtering layer directly contacts the second material; and

the second material does not negatively impact a performance of a copper indium selenide (CIS) based semiconductor absorber layer of a solar cell made from the sputtering target.

2. The sputtering target of claim 1 , wherein:

the support structure comprises a barrier layer comprising the second material formed on a backing structure of a third material that is different from the second material; and

the barrier layer is capable of blocking diffusion of atoms from the backing structure into the sputtering layer.

3. The sputtering target of claim 2 , wherein:

the first material comprises a transition metal selected from a group consisting of Mo, W, Ta, Y, Ti, Nb, Zr and alloys thereof, and an alkali metal selected from a group consisting of Li, Na, and K;

the second material is selected from a group consisting of Mo, W, Ta, Y, Ti, Nb, Zr, alloys thereof and nitrides thereof;

the backing structure comprises stainless steel; and

the barrier layer is capable of blocking diffusion of at least one of Fe, Ni or Cr atoms which negatively impact the performance of the CIS based semiconductor absorber layer from the stainless steel toward the sputtering layer.

4. The sputtering target of claim 2 , wherein:

the backing structure comprises a planar support plate or a hollow support tube;

the barrier layer comprises a foil or a deposited layer; and

the barrier layer is formed between the sputtering layer and the backing structure.

5. The sputtering target of claim 1 , wherein the support structure comprises a backing structure comprising the second material.

6. The sputtering target of claim 1 , wherein the first material comprises the transition metal selected from a group consisting of Mo, W, Ta, V, Ti, Nb, Zr and alloys thereof, and the alkali metal selected from a group consisting of Li, Na and K.

7. The sputtering target of claim 6 , wherein the first material comprises 0.5 to 10 wt % sodium, 0-50 wt % oxygen and balance molybdenum.

8. The sputtering target of claim 3 , wherein the barrier layer comprises:

a first barrier layer comprising Cr in contact with the backing structure; and

a second barrier layer comprising Mo formed between the first barrier layer and the sputtering layer.

9. The sputtering target of claim 3 , wherein the barrier layer comprises:

a first barrier layer comprising Cr in contact with the backing structure;

a second barrier layer comprising Mo;

a third barrier layer comprising Nb;

wherein the second barrier layer is formed between the first barrier layer and the third barrier layer; and

wherein the third barrier layer is formed between the second barrier layer and the sputtering layer.