The Effect Of Nitrogen On The Diamond Films Prepared By Dchot-cathode Plasma Chemical Deposition And Research On Growth Characteristics Of Diamond Films

Compared with the (111)、(110) faces of diamond film,(100) faces have manyadvantages, such as smooth surface、low stress、high thermal con ductivity and thelarge of carrier collection distance and so on. Researching on diamond filmpreparation technology of the (100) faces plays an important on mechanical、thermal、 optics、 electronics and other areas; The effect of N impurity on the growthproperties of diamond films caused more attentions for researchers. The study of Nimpurities existence state on improving the diamond film surface topography、qualityand reducing stress membrane、and further exploring the effective n-type dopingsemiconductor diamond film have realistic meanings. Therefore, in this article weprepared diamond films and optimizated the prepation process by using theDC-PCVD methods. Focus on the nitrogen flow of the diamond film surfacemorphology、 grain orientation、 film quality、 growth rate、 the existing state of Nin diamond film, resistivity and other growth characteristics influence.(一) The study of the effect of nitrogen on diamond growth properties.Using scanning electron microscope、Raman spectrometer、X-ray diffraction,we studied the films surface topography、film quality、faces orientation、growthrateof different nitrogen flow rate. At the same time, we studied the growth properties offree-standing diamond films surface and cross section by adding nitrogen.The add of nitrogen can promote diamond film transformating from (111) facesto (100)facest. When nitrogen flow is smaller, diamond surface crystal faces have nosignificant changes and show (111) faces mainly.(100) faces appeared with theincrease of nitrogen flow. When nitrogen flow increased to a certain amount, diamondfilm present (100) faces completely with good consistency and completely grain. Withthe increase of nitrogen, diamond film still display (100) faces, but the diamond film crystal appear disorder、uneven grain size and grain gap significantly increased, inaddition, the carbon state increased, accompanied by the decrease of diamond filmquality obviously.With the increase of nitrogen flow rate, the growth rate of diamond film andincreased firstly then reduced, the access of a moderate amount nitrogen can make thegrowth rate of diamond film increased by more than30%. With the access ofexcessive nitrogen, the growth rate of diamond film to decline significantly.Using optimization of the experimental conditions, we have perapared free-standing diamond films with1.0mm thickness, a diameter of50mm, what is morefilm center grain size is larger than edge. The diaphragm thickness is much evener,mainly display (100) faces, grain crystalline completely.The longitudinal growth offilm is structural density by columnar growth.(二) Using XPS, XRD diffraction method and four probe method, we studied theexistence state of diamond film with nitrogen impurities, stress、resistivity and othercharacteristics.When nitrogen flow rate is low, the diamond film C1s spectrum in283.6evnearby sp~2C-C key characteristic peak intensity is stronger with the nitrogen gas flowrate increased, exlaining the increase of carbon phase with the growth of nitrogenflow,;C1s spectrum in285.0ev nearby sp~3C-C key characteristic peak strength havenot changed significantly. C1s spectrum in285.9ev nearby sp~2C-N key characteristicpeak strength turn stronger with the growth of nitrogen flow rate, showing that there isN with the state of sp~2C-N in diamond films, and increased with nitrogen flow rategrowth; There is a faint C-O key characteristic peak near287.4ev.When nitrogen flow rate is higher, it appears a N1s spectrum characteristic peaknear399.8ev and401.2ev in diamond films, corresponding to sp~2C-N key and N-Okeys which are stronger with the increase of nitrogen flow rate, showing that thecarbon states have increased, and the adsorption of N strengthed, leading to the increased of nitrogen content.In short, in our experiment condition, C1s spectrum and N1s notation have Nwith the state of sp~2C-N in XPS spectra of diamond films preparated in the range of0-4.0sccm nitrogen flow rate, and sp~2C-N key of the peak intensity increased with thegrowth of nitrogen flow rate.The stress of diamond film preparated by accesing nitrogen show compressivestress which decreased firstly and then increased with the growth of nitrogen flow rate.The minimum value diamond film stress is about1.2GPa.The resistance of diamond film reduced with the increase of nitrogen flow rate,when nitrogen flow rate increase to a certain value, the resistivity droped to the10-1-100. Cm. Increasing nitrogen flow rate further, the resistance drop of diamondfilm is not apparent.