_Applied_  
_sciences_  
_Article_  
Study of Atomic Hydrogen Concentration in Grain Boundaries of Polycrystalline Diamond Thin Films  
[PERSON] 1,2,3,*D, [PERSON] 2,4,5, [PERSON] 6, [PERSON] 2, [PERSON] 7, [PERSON] 8, [PERSON] 4 and [PERSON] 2,9,*  
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nature of the grain boundaries is the same and that the variation between polycrystalline films stem from the difference in the amount of grain boundary present.  
PCD films, ranging from ultrananocrystalline diamond (UNCD) films (2-5 nm grain sizes) to microcrystalline diamond (MCD) films (0.5 to \(>\)1 \(\upmu\)m grain size), have been shown to have important technological applications [1; 2]. Systematic studies involving varying ratios of Ar and H\({}_{2}\) gas flow in standard cubic centimeters per minute (sccm) during the growth of PCD films were performed for both hot filament chemical vapor deposition (HFCVD) as well as microwave plasma chemical vapor deposition (MPCVD) (for example, see references [3; 4; 5] and [1; 6; 7; 8; 9], respectively). These studies were performed to understand the role of gas composition during PCD film growth in the insertion of H atoms into the PCD films and their effect on electrical properties [10] and mechanical properties [6; 11].  
The relationship between the H\({}_{2}\) gas concentration during PCD film growth and the actual concentration of H atoms incorporated in the films has been characterized using Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) as tools to extract qualitative information about H atom concentration on the formation of C-H chemical bonds [8; 12]. To provide more quantitative data, additional analysis techniques have been used, namely, secondary ion mass spectrometry (SIMS) [13], elastic recoil detection analysis (ERDA) [14], and nuclear reaction analysis (NRA) [15; 16].  
These investigations have determined that H is incorporated into the grain boundaries and there is an indirect relationship between the grain size and the H concentration. There is also a wide acceptance that the H is responsible for the Raman spectra associated with C-H bonding.  
The aim of this work was to extend these findings over a large range of crystal sizes and to test the ability of a simple geometrical model to explain the observed hydrogen incorporation and Raman spectra.