The focus of this paper is the application of Fourier transform infrared spectroscopy (FTIR) and near infrared-tuneable diode laser spectroscopy (NIR-TDLAS) as in situ tools to monitor the formation of gas phase products during atomic layer deposition (ALD). Two studies are chosen to highlight the importance of monitoring the gas phase, in this surface driven process, for both mechanistic and reactor dynamics considerations. The first study is the FTIR monitoring of the ALD of HfO(2), from Hf[N(CH(3))(2)](4) and H(2)O where it was found that, in addition to the expected HN(CH(3))(2), gas phase species were generated including CO, CH(4) and HCN. The second ALD system investigated was the growth of Al(2)O(3) from Al(CH(3))(3) and H(2)O employing NIR-TDLAS as a real time in situ probe to monitor the evolution of CH(4). (C) 2010 Elsevier BM. All rights reserved.The focus of this paper is the application of Fourier transform infrared spectroscopy (FTIR) and near infrared-tuneable diode laser spectroscopy (NIR-TDLAS) as in situ tools to monitor the formation of gas phase products during atomic layer deposition (ALD). Two studies are chosen to highlight the importance of monitoring the gas phase, in this surface driven process, for both mechanistic and reactor dynamics considerations. The first study is the FTIR monitoring of the ALD of HfO(2), from Hf[N(CH(3))(2)](4) and H(2)O where it was found that, in addition to the expected HN(CH(3))(2), gas phase species were generated including CO, CH(4) and HCN. The second ALD system investigated was the growth of Al(2)O(3) from Al(CH(3))(3) and H(2)O employing NIR-TDLAS as a real time in situ probe to monitor the evolution of CH(4). (C) 2010 Elsevier BM. All rights reserved.