Light-emitting device and light source apparatus

1. A light-emitting device comprising:

a substrate having a groove extending in a first direction and a first surface and a second surface respectively arranged to sandwich the groove in a second direction crossing the first direction;

a first electrode provided on the first surface;

a second electrode provided on the second surface;

a graphite thin film provided on the first electrode and the second electrode and extending from the first electrode to the second electrode along the second direction in such a way as to be astride the groove;

a third electrode electrically connected to the first electrode and provided on the graphite thin film in such a way as to be opposite the first electrode via the graphite thin film; and

a fourth electrode electrically connected to the second electrode and provided on the graphite thin film in such a way as to be opposite the second electrode via the graphite thin film.

2. The light-emitting device according to claim 1 , wherein the graphite thin film is multilayer graphene the number of layers of which ranges from 50 to 2000.

3. The light-emitting device according to claim 1 , wherein one end on the groove side of the first electrode is situated further on the groove side than one end on the groove side of the third electrode; and

one end on the groove side of the second electrode is situated further on the groove side than one end on the groove side of the fourth electrode.

4. The light-emitting device according to claim 1 , wherein the first electrode extends at least to a border line between the first surface and the groove; and

the second electrode extends at least to a border line between the second surface and the groove.

5. The light-emitting device according to claim 1 , wherein the substrate has a base member formed of silicon, and an oxide layer formed of a material containing an oxide; and

the oxide layer is arranged at least between the base member and the first electrode and between the base member and the second electrode.

6. The light-emitting device according to claim 1 , wherein the third electrode and the fourth electrode respectively have an outermost surface layer, and an intermediate layer arranged between the outermost surface layer and the graphite thin film; and

the resistance value of the outermost surface layer is smaller than the resistance value of the intermediate layer, the first electrode, and the second electrode.

7. The light-emitting device according to claim 6 , wherein the outermost surface layer is formed of gold;

the intermediate layer includes a first layer formed of titanium and a second layer formed of platinum;

the first layer is provided on the graphite thin film; and

the second layer is arranged between the first layer and the outermost surface layer.

8. The light-emitting device according to claim 1 , wherein the first electrode and the second electrode respectively have a third layer formed of titanium and a fourth layer formed of platinum;

the third layer is provided on the substrate; and

the fourth layer is arranged between the third layer and the graphite thin film.

9. A light source apparatus comprising: a light-emitting device according to claim 1 ; and

a package having a light-transmitting window and forming an inner space maintained in a vacuum state,

wherein the light-emitting device is arranged in the inner space of the package.