A Plasma Enhanced Chemical Vapor Deposition (PECVD) device for depositing material derived from a precursor gas, the device comprising: a plasma source, said plasma source comprising: a first electron emitting surface (12, 31) and a second electron emitting surface (13, 38); a precursor gas manifold (17, 37) configured to deliver the precursor gas and a reactant gas manifold configured to deliver reactant gas; a power source electrically connected to the electron emitting surfaces (12,13, 31,38) and configured to supply a voltage that alternates between positive and negative to cause the voltage supplied to the first electron emitting surface (12, 31) to be out of phase with the voltage supplied to the second electron emitting surface (13, 38) and to create a current that flows between the electron emitting surfaces (12, 13, 31,38); such that a plasma is created between the electron emitting surfaces that is substantially uniform over its length in the substantial absence of closed circuit electron drift; characterised in that said first and said second electron surfaces (12, 31; 13, 38) are separated by a dark space (20,33); wherein the precursor gas manifold (17, 37) is positioned so the precursor gas flows in the dark space (20, 33) between the first and second electron emitting surfaces, and wherein the reactant gas manifold (18, 35) is positioned so that the reactant gas flows along the electron emitting surfaces (12, 13, 31, 38). a plasma source, said plasma source comprising: a first electron emitting surface (12, 31) and a second electron emitting surface (13, 38); a precursor gas manifold (17, 37) configured to deliver the precursor gas and a reactant gas manifold configured to deliver reactant gas; a power source electrically connected to the electron emitting surfaces (12,13, 31,38) and configured to supply a voltage that alternates between positive and negative to cause the voltage supplied to the first electron emitting surface (12, 31) to be out of phase with the voltage supplied to the second electron emitting surface (13, 38) and to create a current that flows between the electron emitting surfaces (12, 13, 31,38); such that a plasma is created between the electron emitting surfaces that is substantially uniform over its length in the substantial absence of closed circuit electron drift; a first electron emitting surface (12, 31) and a second electron emitting surface (13, 38); a precursor gas manifold (17, 37) configured to deliver the precursor gas and a reactant gas manifold configured to deliver reactant gas; a power source electrically connected to the electron emitting surfaces (12,13, 31,38) and configured to supply a voltage that alternates between positive and negative to cause the voltage supplied to the first electron emitting surface (12, 31) to be out of phase with the voltage supplied to the second electron emitting surface (13, 38) and to create a current that flows between the electron emitting surfaces (12, 13, 31,38); such that a plasma is created between the electron emitting surfaces that is substantially uniform over its length in the substantial absence of closed circuit electron drift; characterised in that said first and said second electron surfaces (12, 31; 13, 38) are separated by a dark space (20,33); wherein the precursor gas manifold (17, 37) is positioned so the precursor gas flows in the dark space (20, 33) between the first and second electron emitting surfaces, and wherein the reactant gas manifold (18, 35) is positioned so that the reactant gas flows along the electron emitting surfaces (12, 13, 31, 38). said first and said second electron surfaces (12, 31; 13, 38) are separated by a dark space (20,33); wherein the precursor gas manifold (17, 37) is positioned so the precursor gas flows in the dark space (20, 33) between the first and second electron emitting surfaces, and wherein the reactant gas manifold (18, 35) is positioned so that the reactant gas flows along the electron emitting surfaces (12, 13, 31, 38).